There are some things a girl must have before going to the ball - a special dress, some beautiful, impractical shoes and a glamorous hairdo.
When you add on extras such as professional make-up, fake tan, nails and the after party, the cost can soar.
But how much are girls (or their parents) actually spending?
Queens High School deputy principal Di Stewart says the girls are quite realistic with their spending, especially as they may go to more than one formal a year.
[comment caption=Did your formal break the bank?]"I think in general the girls are quite sensible. They share some stuff and buy some stuff. The boys don't all give orchids anymore," she says.
"And now a really nice dress is great. The whole flexibility with fashion has moved into formal. Girls are much luckier that these options are there."
Ginny Orange (17), from Wakatipu High, used to go to a private school in Christchurch and says it cost much more to go to a ball there.
"The tickets were more expensive and you were expected to be more formal. I went to a Christs College one and they had a marquee with a chandelier."
There doesn't seem to be competition over spending between the Queens girls, Mrs Stewart says.
"The girls go along hopefully to feel glamorous. It's important to have a special occasion for that."
• Dress to impress
Ask any girl what the most important part of ball preparation is and she will, without a doubt, say the dress.
This year, full-length numbers have mostly been pushed to the back of the closet in favour of shorter, funkier cocktail dresses (at least in the South).
Sapphire Whyte, from Refind Rig on Great King St, says girls seem to have a preference for simplicity at the moment.
"All of my ball gowns were big, full-skirted and embossed. But girls now seem to like simpler, shorter styles so they can get more wear out of it."
"Short is popular this year and has been for a while," agrees Stax store manager Ann Arthur, crediting celebrities on the red carpet for influencing the move.
"It's not so traditional now. The dresses are funky and they can wear it out again."
Buying it
The first ball may be a special event, but many girls who have already been to one or two can't justify spending so much again.
Alex McPhillips (18), from Queens High School, has been to five formals, two this year already.
"This time I've definitely spent less. Last year's [dress] was $400 in total."
After an extensive two-week search in three cities she found what she was looking for at Pagani for $70.
"We considered sharing dresses, but none were quite right. I like to own one and wear it again."
"Many girls are over it by the 7th form [year 13] and go for cheaper dresses," Ms Arthur says.
"It's easier now to get something good for less money."
Also, shops such as Diva , which sells costume jewellery, give girls a chance to take something standard and "bling it up" to make it unique, she says.
Individuality is an issue - no-one wants to wear the same dress as another girl.
"I saw three girls with the same dress at my formal. Exactly the same," Eliza Sims (17), from Bayfield, says.
There was no embarrassing double-up at the Wakatipu ball, says Ginny.
" I don't think anyone had the same dress. A lot of girls had them made and in Queenstown there's often only one of each dress in the shops."
Second-hand
Another way to ensure individuality is to buy second-hand, either in a shop or online.
Eliza's experience of shopping online is that it's good to have a parent who can sew in case the fit isn't perfect.
"I bought my dress for $60 on Trade Me and my stepmother altered it. We added some blue material to the top and bottom. I didn't want to look like I was getting married."
Melissa Austen (15), of Columba, and some of her friends bought dresses from Refind Rig, which offers both new designer labels and high-end second-hand clothing.
"It was pretty cheap - only about $150. I didn't really want to spend much. For the 7th form I would buy a more expensive dress and have my hair and make-up done."
Having it made
Dallas Cunningham, designer at St Clair Design in Bond St, says quite a lot of girls choose to have a dress made.
"They may buy one off the rack here and have it altered from $189 to $399. If someone's getting one made it's more and they don't blink an eye."
The price of the dress depends on how much work goes into making patterns, toiles (a prototype) and the details, such as ruching and pleats.
One of Ms Cunningham's most expensive dresses cost $400 (excluding fabric).
"The girls are always very grateful to their parents," she says.
Ginny had her dress made in Christchurch - "I designed it myself. I had seen other dresses and knew what I wanted."
Her dress - full-length emerald green satin - cost $350 (excluding the fabric), but she was very happy with it.
"I didn't spend over the top. It was worth it because I had heaps of fun."
Eliza said many of her friends had dresses made by a parent, but one girl spent around $200 getting one professionally made.
"If they had to spend their own money I doubt they'd be so intent on it."
DIY dress
For those with some creativity and sewing skills, making it yourself is a good way to stand out and save some cash.
Laura Bulk (17), from Queens High School, made her own skirt.
"I took sewing in year 9 and 10 so I learnt the skills then. It's nice to make your own things. It makes it special."
And cheaper.
Laura bought the bodice of her outfit from a second-hand designer label store in Australia for under $19 and the fabrics for the skirt cost less than $20.
"I only needed about half a metre of each."
• Other expenses
Hair and make-up
While some girls opt to do their own hair, most turn to a professional to get something a bit more glamorous.
This year, formal hair is still about the curls, either up or down, say staff at Lainie Scott Hair & MakeUp on George St.
Many girls bring in pictures (the big curls of Lauren Conrad from The Hills are big this year) for inspiration.
Hair styling and make-up each cost $60.
Styles at Headquarters in the Centre City Mall range from $55-$75 depending on if it's just a curl or straighten, or if it's a more elaborate look.
Some salons offer special deals for formal-goers.
Why Not Hair in Albany St will do hair and make-up for $85 and include a spray tan for $120.
But one of the busiest places to be on formal day is the Arthur Barnett beauty department, in particular the MAC counter, where places fill up fast.
"Girls book as soon as they know the date of the formal," MAC counter manager Tiam Safari says.
"We had Columba girls booking for the June formal in January."
On the day of a formal they have bookings from as early as 10am and have five staff members working, she says.
Most of the counters offer formal make-up, with the cost of the deposit redeemable in products, so the girls can take away at least some of the things used on them.
At MAC, they pay a $90 deposit and get an hour with a make-up artist as well as details on what has been used and how, and some of the products.
"False eyelashes are popular. And everyone needs a lipstick or lip gloss to top up at the formal," Ms Safari says.
Shoe business
After shelling out for a dress and the hair, it seems many girls want to save on shoes, either buying cheaper options or wearing shoes they already have.
Eliza got her shoes from Number 1 Shoes on Great King St for $20.
"Everyone I knew got shoes there - even the guys. It depended on whether you wanted to spend money."
Perhaps a wise decision considering how long the girls seem to wear them.
"I wore them to the place, wore them as long as I could, then after about an hour I put them in a locker. So many people were barefoot," she says.
"It was the first time I'd ever worn heels. I should have practised a bit."
Melissa also bought her shoes at Number 1.
"I wore them up until the photos then took them off."
Tanning up
Extras such as a fake tan have become popular in recent years, both DIY and professional jobs.
Eliza used Johnson's Holiday Skin to build up some colour gradually.
"I'm really white and didn't want to blend with my dress."
Others were not so keen to trust themselves. Ginny paid $65 for a spray tan in Queenstown.
"I had it properly done and was happy with the result."
The boys
While perhaps not in the same league as girls, the boys are also spending up.
The occasional boy may buy a suit, but it's much more common to hire one, especially as some boys don't want to wear the same suit to more than one formal.
Haley Videler, of Ace Suit Hire, says conservative suits are big this year, though the firm does rent the occasional white, red or blue suit.
"They often don't know what they want so they bring their partners, mums or sisters."
It costs from $250 to buy an ex-hire suit or from $79 to hire a shirt, tie and suit. Shoe hire is an extra $10.
Some boys still buy their partners a wrist spray, which costs about $30, although it's not as popular as it used to be.
"A lot of people did the corsage thing and there was the odd rose here or there," Ginny says.
Photo finish
And of course all that effort needs to be recorded for posterity.
McRobie Studios took the photos for Bayfield and Queens this year.
"We try to make it fun to be there and help them relax a bit," photographer Ray Dustow says.
"If they're having fun they'll come back for more photos."
And the more photos they're in, the more prints they may buy later.
"Six photos is not unusual. Some buy two and some buy 15," he says.
Alex planned to have lots of photos taken with her friends and to buy at least 20.
"It's the last year of school and being with my friends," she explains.
Eliza isn't so concerned about the photos.
"I'll probably just get one. I wasn't in many and I didn't get any with my partner."
The after party
Often creating more excitement than the actual event is the after party.
These days they are organised events - which means buying tickets and maybe even another outfit.
Staff at Stax and Principals say girls often come in wanting to buy another dress for the after party and will happily spend over $100.
Others view the after party as a chance to be more casual.
Bayfield had a rave-themed after party at Sammys, with tickets costing $25.
"Most people wore something white or fluro. I spent about $35 in total. It was DIY stuff more," says Eliza.
"And definitely no high heels."
Wakatipu High had its formal in a marquee near Remarkables Park, with tickets costing $35.
"Everyone changed into casual clothes," says Ginny. "Both experiences were important."
The girls
Ginny Orange (17)
Wakatipu High
Years 12 and 13 formal at Memorial Hall
Ticket: $75. Dress: $350 plus fabric. Accessories: About $40. Hair: About $60. Make-up: About $20 Spray tan: $65. After-party ticket: $35. Photos: $45. Total: more than $690.
Laura Bulk (17)
Queens High School
Year 13 formal at Otago Museum
Ticket: $65. Dress: $19 for bodice. Less than $20 for skirt fabric. Hair: $20 to get curled. After-party ticket: $20. Photo: Most likely just one, $6. Total: $150.
Alex McPhillips (18)
Queens High School
Year 13 formal at Otago Museum
Ticket: $65. Dress: $70. Shoes: $40. Hair: $65 for a cut. After-party ticket: $20. After-party outfit: $30. Photos: Most likely about 20, costing $120. Total: $410.
Melissa Austen (15)
Columba College
Year 11 formal at Larnach Castle
Ticket: $70. Dress: $150. Shoes: $40. Nails: $35. Total: $295.
Eliza Sims (17)
Bayfield High School
Years 12 and 13 formal at Otago Museum
Ticket: $50. Dress: $60. Shoes: $20. Hair and make-up: $20 by a friend. After party: $25. After-party outfit: $35. Photos: $6. Total: $216
