There have been many lucky wild horses that have found their way into the lives of very loving families. There are a lot of wild horses still out there needing that chance to live a life free from fear. Unfortunately, some wild horses that do not find good homes are sold for slaughter. This is wrong.
In Utah, where I live, seagulls are protected, not because of their small numbers but because of their historical significance to the state. In the same way, we as a country should protect our wild horses, instead of turning them into a "cash crop."
It may not be "cost-effective" but cost-effectiveness is not always the goal and role of government. No doubt Yellowstone would fetch handsome prices at auction to private land developers.
Wild horses are much more like Yellowstone than cotton. We should preserve these horses, and the important part of Americana they represent.