Wow you guys are getting ripped off. There are no additional formal training requirements to go from commerical to CFI. Buy a ground school kit ($300-500), find a CFI buddy with 2 years in(initial signoffs), get the damn thing in a week. Its not that hard and you shouldn't have to pay a pilot mill for the extra training. $4k is absurd. $10k is downright robbery. Its not that hard if you are fresh out of training. Of course, it doesn't hurt to do your commerical training from the right seat either.