I'm reminded of a personal story:
Story 1: A number of years ago, I had a modified car, which some bolts on the exhaust would work themselves loose after about 6-12 months. It was annoying to deal with, but took maybe 15 minutes, crawling under my lowered car, in hot/cold weather, on the pavement, etc, trying to get a good angle. On a lift, it would be a 2-minute job at most. One time I decided to just coat-wire it up, and drive to a local shop, and just ask them to deal with it. They said they'd have to give me a quote (weird) , and an hour later they told me "that'll be $800" me "It's just a couple bolts, I've done it before, and it takes me about $15 without a lift. Are you sure?" Them: "Yes, $800 to bolt it up." me: "Ok, I'm just going to go pick up my car." And sure enough, the job took me about 15 minutes.
Story 2: Back to scuba, I had an incident where a scuba-shop condemned a tank I brought in for VIP, because of the manufacture date. TLDR: There were about half-a-dozen things wrong with that story,
and you can read the full story here. Now, I'm about 50/50 on whether I'll take the stupid VIP class, or just print some stickers, because pretty much everyone I talk to who has the VIP qualifications says it's a giant scam.
Anyway, my point being, if I know how to work on my car, regulators, BCD, etc .... then I'm just going to do it myself. And every time I get screwed, I often have to learn 25% to 50% of the job to double-check their work, which means I'm not that far off from learning how to do it myself.