ARBs runs deals sometimes where you can get a free compressor when you buy a locker, not sure how often though. I got gears at the same time as my locker so the only labor they charged me was wiring and installing the compressor (like 1 hr). I would say the labor would be ~$500 if you're not doing gears with it (which now is the best time to do that if you're running bigger than stock tires). What kind of vehicle is it going on (I don't see a current 4runner in your sig line)?