A portion of the FSA costs are the procuring, maintenance, and costs of instruction at longer intervals on campus*.
There’s also the factor of maintaining sufficient engineering labs/facilities for all cadets to fulfill their core engineering requirements regardless of major. A friend at an FSA recalled all cadets had to take a minimum of 5 engineering courses to fulfill that requirement when he was there…even if one was a humanities/social science major.
There’s also the factor that FSA cadets spend most of their summers on military training tours/cruises…including costs of travel to/from those bases/ships.
ROTC programs do have their own costs…but they’re not likely to be anywhere near as extensive as those for the FSAs.
- I.e. Ships for instructing Annapolis/Coast Guard/USMMA midshipmen, aircraft for USAFA students looking to pick up their first pilot license, military assault/training grounds for cadets and instructors, weapon ranges/weapons/instructors, etc.