I like what my area does for Senior "Post" Prom. They rent out the largest hall in the county, and the entire county is invited to attend. For the arrival, it is timed, by school. You are driven to the entrance, introduced, and you walk a red carpet up to the entry to the venue. Parents and family are encouraged to attend, be the "paparazzi", and then leave. A local TV station broadcasts the event, complete with interviews of some of the seniors. It is all very Oscar night like. The year my daughter went, there were 1500 in attendance from 9 area schools. My daughter's school treated it like senior prom, but other schools also had their own.
Tickets are $35 each. Yes, there were many that spent a lot on other things, but my daughter found a great dress, got alterations for a song, and went out for dinner before. They had a great time, and for what she got, I thought the cost was very reasonable.