When the occasion fails to justify the outlay, one acceptable alternative is to hire a dress and the accessories. There are many dress hire shops from which to choose, with stock usually ranging from the eternally reliable dresses made by Bernshaw to little black frocks and creations by the more expensive designers.
Most shops guarantee to clean every item between hires, and this cost is included in the hire charge, but there are less reputable shops that may put a dress straight back on the rail with just a brush-down.
Douglas Griver, managing director of After Dark in north-west London, says: 'We spend four figures a month on cleaning our clothes. Of course, before they are ready to hire, they have to be spotless and in perfect condition every time.'
He stocks, as do most shops, new-season designs, and changes stock every six months, selling off at discount. Sizes range from 6 to 20. You might find something by Terence Nolder or Belville Sassoon.
Hire charges go from pounds 39 to pounds 200, although average charges are from pounds 60-pounds 90. 'We are very flexible on how long someone can keep a dress, although it is usually for a weekend or for two or three days,' says Mr Griver.
Handbags can be hired for pounds 5 to pounds 10; gloves pounds 5; capes or jackets pounds 15-pounds 25; jewellery pounds 3-pounds 15.
Mr Griver takes a deposit of pounds 100, or the number of your credit card, to cover any unforeseen calamities, which he says are very few and far between. Most marks can be dealt with; even cigarette burns can be cut out and invisibly mended or a new panel can be sewn in.
The dress hire companies will tell you that whatever you hire is automatically covered by your home insurance policy, but for how much, and exactly what for, depends on the policy.
At Commercial Union, for example, you would not be covered for all risks, but as long as you informed them, the premium would be between pounds 10 and pounds 20, depending on the dress.
According to Paul Lowin, marketing superintendent of Guardian Royal Exchange, you would be covered under your personal belongings cover (all risks) if you have that cover. If not, and you are worried about replacing a costly dress, GRE's minimum premium is pounds 10.
There is usually a single article limit: in GRE's case, pounds 750. Says Mr Lowin: 'If someone phoned up beforehand asking to extend this to pounds 1,000 for one dress for one night, we would probably be happy to increase the limit for no cost.'
Generally, hiring customers seem to be fairly reliable about returning the goods, and most shops are quite relaxed about when. But Sarah Marques and her partner Louise Eyre of 20th Century Frox in the Fulham Road in south-west London are strict on timekeeping. They take a pounds 150 deposit and hire the dress out for three days. If it is kept longer, the penalty is pounds 10 a day. If you want the goods for more than that and say so at the time, it's an extra pounds 5 a day.
Miss Marques says her customers can also make a pounds 5 insurance deal with her to cover things such as cigarette burns or nail-varnish stains. In cases of serious damage, the repair bill is sent to the customer or taken out of the deposit. If the dress cannot be hired out again, or sold, 20th Century Frox keeps the deposit and the customer keeps the dress. Other shops ask the customer to buy the dress at a reduced price.
Pumpkin Ballgown Hire in the centre of Manchester, owned by Sandra Levin and Jane Myers, stocks over 600 dresses. Charges are pounds 45 to pounds 95 for four nights, and they say they are flexible about the length of hire. There is a 15 per cent reduction for students.
They have their own dressmaker for alterations, jewellery can be hired from pounds 10, shoes from pounds 8 and jackets from pounds 15.
Gown and Out, with branches in west London and Bourne End, Buckinghamshire, hires out dresses in sizes 8 to 28. A simple black party dress can cost as little as pounds 15, while a Bruce Oldfield could be pounds 90. Barbara Wilsher, the owner, said: 'Although people who could afford to buy are now hiring, the people who used to hire for company functions are doing it less, mainly because there are fewer parties and lots of people are just making do.'
There is no deposit needed at Cinderella Designer Gowns, with 10 branches in Scotland, but hire charges are similar. 'We expect our clients to use their own insurance to cover any repair bills. And we have only had two late returns in six years,' says Gill Greehalgh.