I've collected some "typical" cost data for FLL,VRC, and FTC. The FLL and FTC cost data came from FIRST WA and USFIRST sources, and the VRC data came from me
(we are in our fourth year running a multi-team VEX program, so I consider "me" a pretty reliable source). I've included FLL as it is FIRST's middle-school program, and VRC is also used by a number of middle school programs.
Disclaimer: Like Rich Kressley, I consult for IFI.
I estimated costs for a classroom-sized team with four robots for all programs, and estimated costs for the initial year of competition, and then the second year when fewer parts must be purchased. None of the cost estimates include shipping or taxes. Link to spreadsheet:
http://www.chiefdelphi.com/media/papers/2285
First year cost estimates for four teams:
VEX Robotics Competition: $3,596
FIRST LEGO League: $3,095
FIRST Tech Challenge: $6,796
Additional year cost estimates for four teams:
VEX Robotics Competition: $800
FIRST LEGO League: $1,365
FIRST Tech Challenge: $2,796
If you go to the linked spreadsheet it is pretty easy to change the values to ones that seem good to you. I hope you enjoy playing with the spreadsheet, and make sure you look at the "Expense Graphs" tab, too.