It shouldn’t cost that much. Maybe try a less expensive vet’s office. We had BOTH our house cats fixed AND all their shots for around $200.
And there are sometimes cheaper spay neuter clinics just for ferals and barn cats through the humane society.
We’re looking into one of those city-funded low cost spay & neuter clinics now; I hate to take her to a discount surgeon, but it’s better than adding to the feral cat population around here, I suppose.