I think you have several optons:
First, is something wrong with the way the regs are working, if not keep diving them, some models of regs can go years/100's of dives without servicing (that said some don't)
Second option spend even more on a course form Steve buy the tools and only have to buy the parts kits from now on. Probably your cheapest option in the long run
Third - Pay Steve his rate, I haven't used him, but I have seen his shop and beleive he will do a good job (which is not always the case)
Forth option - If you can get a set of regs for 25% less than what you were quoted for the service buy them. It sounds like you got a killer deal, I doubt you get it again, in which case your point about the cost is invalid
Fifth option find a someone to do it cheap, you might get what you pay for. Rebuilds/servicing although easy amazingly enough seems to get screwed up in the US with astonishing regularity.