The guy charged me $261 per GFCI, for a total of $783. He spent an hour to
do the job. I told him before I signed the work authorization that this
seemed expensive and asked about a discount but he just frowned. Is this
really a fair price?

No.


Their yellow page ad reads "reasonable prices" and "complete professional &
reliable service" with "30 years experience!!"

You might be able to sue them in small claims for false advertising.
Emphasis on 'might'


i have no one to blame but myself, but do i have any recourse?

No.


Can't i just call the guy to complain and ask for a partial refund?

You can ask, but it probably won't do you any good.


Or can I really win in small claims?

Unlikely.


yes, I deserve an award for stupidity and gullability

If you thought it was unreasonable, why didn't you get a second quote?