Vanier College in Montreal is where I had Ted done. The neuter was $40 and the vaccinations were $30. I think they charge $70 to spay a female. Are there any veterinary colleges near you? If so, I would inquire as to whether they do a spay/neuter clinic. Most do since that's how students get experience. $400 to spay a cat is robbery in my opinion, especially since you adopted her from there. My local vet charges around $100 to adopt a kitten and the spay/neuter, shots, worming, and blood work are already done when you get the cat.
Vanier Phone number in Montreal - added by Marko - 450-458-0333