If your rabbit or cat is healthy, then yes, the "cheaper" spays are generally ok. But a more expensive spay is generally safer... they do bloodwork, have different monitoring methods in place, etc.
We have a vet here that will spay for $150.... but he also admits that the rabbit is more likely to die on the table because he doesn't do preoperative bloodwork, and does not have the specialized equipment to monitor the rabbit that the specialty exotic clinics have.
He says if the spay goes well, that may not matter, but honestly, if there's a problem, he wouldn't be able to screen that out beforehand, and he likely couldn't bring the rabbit back if there were problems with anesthesia. He is an excellent vet, and I trust his opinions on many things, and he feels like it's important for there to be a cheaper option so more people do spay their rabbits -- and I agree.