The class parents of the current graduating class hosts the After Prom. They start fundraising during that class's freshman year and continuing through senior year. I have heard they typically need to raise $30K - $40K, but only hearsay as I've never been directly involved with the committees - I just participate in the fundraisers. They usually sell tickets for the After Prom, with a cost around $20.
Some places that they've held After Prom:
A water park (it's over an hour away). They ride a bus that leaves around 11:30 PM, go to the water park and have free use of the water park all night. The bus then leaves at 6 AM and takes them back to the school. They have snacks on the bus on the way there and back. At the water park, they get a voucher for food.
A local sports park. They have carnival style games, casino tables (with fun money), they have food trucks and inflatables. The have use of the indoor soccer field, batting cages, golf, basketball.
At the After Prom events, students are usually gifted cash of any excess money collected by the After Prom Committee. I'm not as familiar with other items they raffle off.
For fundraisers:
Parents who volunteer at concession stands or the apparel shop at the high school earn money toward the group of their choice - a parent can choose After Prom or their child's sport, band, etc.
Selling 50/50 tickets at home football games (different organizations take turns selling the 50/50 and get a donation)
Football squares - Super Bowl or "big" college games (this is an easy fundraiser as nothing really to do except sell the squares and draw numbers).
Paint and sip nights - Drink wine and paint (a painting, a wine glass, etc.)
Custom tumblers - a local Mom makes custom drink tumblers with the high school logo - you can add your child's name, graduation year, sport or band.
Scentsy fundraisers - one of the Moms is a Scentsy rep and donates some proceeds
Pure Vida bracelets - with the school colors
Dinners - a local catering facility offers dinners for 4-6 people for pick up on a weeknight. The committee receives $10 or $15 per dinner from those sales.
Dine to Donate - We get X % of sales on an assigned weeknight from the restaurant
Food Sales - Our local committee sold pepperoni rollers before Christmas this year.
Craft Fair - the committee hosted a holiday craft fair. Vendors paid to rent space, ticket sales at the door, pictures with Santa and food sales on site (this is one of the largest fundraisers)
Reverse Raffles at a local banquet hall - with basket auctions (all baskets donated by the parents) (this is also one of the largest fundraisers)