America's new millionaire class: Plumbers and HVAC entrepreneurs

I wonder if that's the reason my HVAC guy tried to charge me $700 for running a thermostat cable less than 8 feet (that I later did myself in less than 30 minutes).

This is the typical trade tactic for rejecting a job that is too small to be worth your time. He still has to come out to your place, with his truck and tools, and install that 8 feet of cable. He could spend that same overhead doing an 8 hour, much more profitable job.

So he bid an outrageous amount. If you had said yes, he covers his overhead. If you reject it, he does something more profitable with his time.

RE ".... If you had said yes, he covers his overhead..." Really - a overhead of several hundred dollars. Seems far fetched to me.

It takes time (plus money) to drive all over the place giving quotes for simple jobs that people end up getting multiple bids for and/or end up not hiring anyone in the end. Those costs aren't provided as charity, but rather has to be baked into the price of the jobs that do get accepted.