Addict
Your LDS's are threatening to stick it to you so you think you will knuckle under - another LDS success story. Are you really going to be satisfied with that?
There are other options for service. This operation in CA looks like it will do the work.
http://www.diversdiscount.com/resources/frameset-search.asp
I recall another in FL but don't have the link handy. There prices are in line with what Mike F is saying and not entirely out of line with what your LDS is quoting. Even LP will do the servicing. Another option is to send it to the mfgr. Scubapro spells that out as a specific option in their users manual.
The rub is what they are really going to do for that price. With some LDSs, that should be a major concern. Are thay going to do what Mike described, or will they take some shortcuts? And how will you know.
I do my own & I don't have a lot of experience. I 'service' my reg often (monthly or more). But that service is usually visual inspection, check IP & dive it. Sometimes I'll also fill the sink and check cracking pressure. During the set-up and dive I'm "checking" for leaks and performance. After a SW dive, I put it in the tub and check for leaks and maybe cracking pressure. In 4 years on my Mk20/G500, I have inspected,dissassembled, cleaned, inspected, lubed, reassembled, and inspected the Mk20 twice. No parts used yet. I've also adjusted the G500 twice in that time - no dissassembly beyond that needed to adjust. When I did disassemble the Mk20, it took me a couple hours. The point is, you may think you are getting a full annual service, but when the bill is only $35.00, they may have just inspected and adjusted it and are now betting your satisfaction (and maybe your saa) that it will go another year. Or the bill may be the full $100.00 and still little was actually done.
Your LDS has clearly shown that it doesn't mind ripping you off. I know I wouldn't trust them for much more than an airfill. If you can't find someone you trust, at least find someone who isn't overcharging you.
Too bad Mike won't do MO service.