Different hospitals will price their services differently. Some will have higher prescription costs, others higher exam fees, but in the end it typically evens out. I would ask how often they see rabbits in general and how often they do spays on rabbits. If they ask you to fast your rabbit, make sure the instruction is coming from the vet (sometimes the receptionists don't know). If the vet asks you to fast your rabbit, don't go.
The spay may also include different things in the price. For example, some vets include pain meds and some charge extra for them, but I would make sure you're getting pain meds.