at our ex farm, we used the "equine dentist" that the BO called in. I was horrified when it was all over. He was fat, with a long greasy ponytail, told off color stories in front of the other boarder's two young daughters, stuck his hand in the horse's mouth and started filing away without EVER actually LOOKING in there....he just felt around, decided what to file and moved on to the next horse. The floating took less than five minutes. Seriously. From start to finish....five minutes.
And he only charged $35 dollars.
You get what you pay for.
My equine dentist does not sedate unless it is required, and then a vet has to be called. I have never had it be required, he feels the teeth and does it by hand. For teeth that are not too bad, he is done in around 10-15 mins.
OP I do think that's in the ballpark for how much vets charge. The barn call fee, sedation and extra cost for power floats are all normal for a vet.