Just planned a VEX STEM camp out for the summer, ended up being $200 per student, 9-3 PM with lunch for 25 roboteers.
- Food - providing water (est is 4 bottles per day per person (camp is in July). Cut up fruit chunks for the morning (watermelon, cantaloupe, oranges,) , crunchy (carrot, celery, broccoli, apple, and something else) for the afternoon. Lunch is sandwiches, chips and a cookie. Check your local grocery, for small groups they are a decent price. You'll need to pick up the food. Coolers with water and ICE!!
-- Materials -- Each roboteer is responsible for bringing their own VEX parts. We'll have some extra battery sets.
-- Handouts, about 75 pages per person.
-- Adult instructors (~$30hr)
-- Site fee to cover cleaning, trash removal, etc.
We are doing VEX building from the ground up using the 2016-17 game if we have the parts, otherwise will do CleanSweep since I still have those elements. Goal is to be able to run a small 1v1 event the afternoon of the last day.
More details on what you want to do would be helpful.
I'm planning a similar event, a little more expensive since we will be doing Arduino's and the kit that I want to use is $45 per person.
Gadget Cat Arduino starter kit