First of all, you can easily do a class party for 10 kids for under $20. Chips are 99 cents a bag, juice (the gallon jug of Hawaiian Punch) is $2, you can buy a box of 12 cupcakes at BJs for $9. You don't need paper plates or cutlery. Napkins are $2/bag. Cups $1 pkg... Add it all up. Even with 5 bags of chips it only comes to $19. Music is free since someone can bring in a radio (although most teachers have them in the classroom anyway) and games are free since kids can bring them to school or you can make up a game to play.
As far as receipts... you're darn straight I want to see a receipt. If you're going to tell me with a straight face that it costs you between $80-$190 for a class (19 kids) party, you better be serving a full meal, including appetizer and dessert. However, most class parties consist of juice, chips, cupcakes and the like. I also don't think any teacher deserves a $380 "gift". That is absolutely absurd which is why I refused to send in the money for that.
If it's costing you money out of your pocket, then you're doing something very wrong.
Oh, and I can't be a "class parent" since I work full time.