Calling that a monopoly price shows ignorance on what a monopoly is. Even large metropolitan areas have just a handful of emergency vet hospitals. Emergency vet hospitals don't have an army of vets on standby to handle cases. 2-3 is common and they might be just interns/residents supervised by a more experience vet. Scarcity and lack of supply have a much greater effect than collusion.

Pet owners should know this before getting a pet, or properly plan.