Behavior is adversely affected by surgery. The only change in behavior is positive. Male cats tend to reduce territorial spraying, depending on their age at neutering. Neutered dogs and cats fight less, resulting in fewer battle scars, contagious diseases and abscesses. They also wander less because they aren't as interested in pursuing females in heat.
Animals become fat and lazy after spaying or neutering.
In fact, one unaltered male can be responsible for impregnating dozens of females. I don't need to spay my dog because she is always kept in the backyard. Males will jump fences they wouldn't normally jump, just to get to a female in heat. The Yuba Sutter SPCA runs a low cost clinic so it doesn't have to be a major expense. And you can't put a dollar figure on lives destroyed because there wasn't a home for them.