swinnea
Feral cats are a huge problem here in Florida. Many counties now encourage catch, neuter / spay and release instead of euthanasia. There's a place (the acronym is PAWS) in my county that does neutering and spaying plus shots inexpensively.
Mina was the last one I brought there and they spayed her, checked for FIV and Feline leukemia, gave her all of her shots (rabies etc.) for $60.00. We brought her brother Squint to our Vet and it cost $258.00.
If you just did the spaying and neutering it's something like $10.00 to $20.00. What they do then is clip the tip of one ear which is the universal sign that the cat has been fixed etc. and is therefore not a problem as far as reproducing more unwanted kittens.