The fees are high in part because it's a govt run low volume program that must at least try to pay for itself. Flight examiners aren't getting rich.
I'm working my way through paperwork to get my CFII (military equivalency exam and no practical, FTW!) but there isn't any realistic way that I could make a good living just as an instructor. I plan on using my CFII as a way to get other people to pay for my flight time while I'm a military UAV driver, but it sure isn't going to pay any bills. I'll actually probably lose money because I'll need to teach myself the FAA approved methods of instrument flying. The military techniques are in some cases almost exactly opposite of the FAA approved stuff, especially where it comes to control and performance and which instruments are "primary" and "secondary" during instrument flying. Military flight instruments are on average more reliable and things happen much quicker, so we focus primarily on the attitude indicator and power setting as "control" instruments, then monitor airspeed, VVI, altimeter, and hdg as "performance" indicators. The FAA does it pretty much the opposite, which is confusing to the poor old military pilot

So I'll probably end up losing money as a civilian flight instructor but it will be cheaper than paying for my own hours once the military tells me to hang up my G-suit for good.