20 years ago, the going rate for installing a socket in an existing wired and ready to go junction box was $50. It's about a 5 minute job. I know it's about 5 minutes because I've done a lot of them myself.
I'm sure prices have gone up a lot in the last couple decades.
They are charging for their time to drive to and from you, the possibility that the job is more involved than described, and the liability from doing the job. And the opportunity cost of not accepting a different job due to your job.
If I hired one to come out and do one socket, I'd be sure to get a $200 site visit charge added on.
He's probably got a backlog of large jobs he can make more money on. So if he's going to come out and do outlet installation on one house, he's going to bid an amount that is worth delaying other work.
For small/simple household jobs, you should call a handyman not a trade contractor.
In some jurisdictions you may be able to get away with one GFCI outlet per circuit, but then you're paying for their time to map out which circuits are which.
As in, they're probably not working steadily, 40 hours a week, every week, but they still have bills to pay, and this down time must be factored into their rates for the profession to be sustainable.
On the other hand, if they DO work 40 hours a week, every single week, they can probably afford to raise their rates...
Have not been an electrician, but I have been a software contractor, and the idea is the same.
But the reality is they've also got the businesses expenses of maintaining their work vehicle, their insurance, their healthcare, etc. That $50 probably only translates to $20 into usable income.
He gets the bill and says "That's outrageous, that's more than I make as a doctor".
The plumber replies "Yeah that's more than I made as a doctor too."
I was pretty happy to pay the 4 or 5 times what the day rental for machine would have been. Took em about 25 minutes.