I have helped with lots of balls / Burns Nights / Skool Discos and the like.
Ticket price more or less covers fixed costs.
Profit tends to come from raffles and auctions.
Many people who will not / cannot buy a ball ticket will buy raffle tickets for the draw taking place there, but to sell in advance you need to have tickets printed at a cost of about £80, and obtain a lottery licence (about £40.)
To use 'cloakroom tickets' (the coloured, numbered, pre-printed tear-off tickets you buy in books) a school does not need a lottery licence but cannot sell in advance of the occasion, only on the day.
Many local businesses will donate something as a prize though - meal for two, grocery basket, blow-dry, etc.
To do a cheap and cheerful ball, try the 'Glyndbourne' option: use the school hall/church hall, supply tables, cutlery, and decorations; hire a disco. Guests bring a picnic basket (can be as elaborate as they like) and their own wine/booze. You will nee a Temporary Events Notice for unlicenced premises. Can be done for between £7.50 an £15 a ticket depending on numbers and how elaborate you want to be with tablecloths, candles, balloons, etc.