"The reason you don't do it to males is it's a waste of money, (except for getting rid of the Tomcat attitude and marking)."
I think Henning is referring to neutering Toms but didn't see what the reference was to. I work with feral colonies and I've come across many really beat up toms over the years. After getting them fixed they often turn out to be grateful and loving creatures. Many have been socialized earlier in their lives and got dumped for whatever reason. The recession caused many people to have to move and the bastards just left their pets behind to fend for themselves, both cats and dogs. Some of the toms have missing eyes from fighting. All have torn ears. Most have open wounds that are infected. Their immune systems can carry huge toxic loads, at least for awhile. Getting them fixed relieves them of their hormonally-driven behaviors and gives them a chance at some pleasure in life.
Females can become pregnant as early as four months. They're still kittens yet have to take on the physical stress of birthing and nursing before they even know who and where they are. While nursing they can (and do) become pregnant again, over and over. What happens to their kittens? The same thing that happened to the moms. Nature doesn't care about individuals, only the survival of the species - hence the insane breeding cycle cats are victims of.
I take pleasure in life helping to allieviate this cycle. I trap these cats, get them fixed and then maintain the colonies they came from. I've found homes for many of them and given a home to others for many years, almost always kittens. The ones I've given a home to are fortunate in that my property is large enough and safe enough from predators that they live indoor/outdoor lives. No litter boxes. No smells. They are very lucky cats and so am I.
Cats are really clean, interesting intelligent creatures. Dogs are the same but I couldn't live the life I live were I to try and help dogs as I help cats. They're too dependent. Cats can be left for days at a time and will greet me with enthusiasm when I get home, but they were fine without me. Not so with dogs.
Just wanted to say it's important to neuter the toms along with spaying the females. It's certainly not "a waste of money." Regarding cost, with a little looking one can find vets who will do low cost spay/neuter. The ones who charge $100 and more, sometimes much more, should be boycotted.