I think my vet charges around $40-$50 for a neuter and around $50-$70 for a spay. A spay is typically more because it's a more complicated procedure. It's been awhile since I had my cat fixed, so I can't remember exactly.
Prices seem to vary alot, I would call around and see what your local vets charge. If you know people with pets, asking them what vets they see would be a good starting point.