Besides it is much cheaper to clean the pen and feed them for four days. Dog food is pretty cheap and it doesn't really cost that much to have someone come by once and and hose their cage out. I doubt it cost more than $20 total. Everything else involved cost more. Not mention it would inhumane as hell to turn a dog out on the street immediately after surgery. Even if it cost $50 a day to keep the dog you wouldn't save much since you would need to keep the dog until it recoverd.

Of course the entire discussion is rather pointless since the role of animal control is to remove stray animals not just sterilize them and then turn the loose on the streets to roam our neighborhoods. With thinking like this I can see why you became a liberal.