Usually, a fireworks show in homecoming would be a fireworks finale. You may have heard "grand finale" a lot pertaining to fireworks. But these fireworks would last 3-4 minutes long. Probably 500 to 750 aerial shells are used in a typical show.
If the shells are used at the consumer-level, it is close.....$5,000. That is, from 4" to 8" shells. That is if the pyrotechnicians are amateurs, like those from Pyrotechnics Guild International (PGI).
If they are using the larger professional fireworks, such as 24" and "32" shells, the show could cost $20,000, and probably $250,000 for liability insurance coverage and also to cover costs for a fire marshal to inspect the professional fireworks.....just in case the fireworks show goes array at any part of the show.
All together, that show could cause $270,000.