My home warranty insurer sent All-Star Appliance Services to my house to service my furnace, which was performing poorly.
The tech accepted our $100 deductible, looked at the furnace, and said that we needed coil cleaning, which wasn't covered by our home warranty insurance. The owner of the company estimated that it would require:
* Another round of diagnostics using a scope ($100)
* Coil cleaning ($250)
* Cutting a hole in the side of our furnace to install a panel for future service ($150)
Altogether, $500 - on top of the $100 we'd already paid.
I called a tech from another company, who came out and fixed the problem in five minutes for $2.00 in parts. We'd been using the wrong furnace filter. The coils were fine, and the $2.00 repair cost completely fixed our problem.
I asked the second tech why All-Star hadn't caught that and wanted to charge us $600. "No idea. Checking the furnace filter is ALWAYS the first thing you check because lots of customers make that mistake."
I don't know whether All-Star Services is grossly incompetent or committing outright fraud... but in my case, it certainly looks like those are the two options.