Bison are not and have never been a hard animal to hunt. How do you think they managed to shoot them by the millions? That being said, I've shot a few heifer cows for meat because you really can't beat a young bison for table fare. Since most bison are taken off big private ranches, the exceptions being the Henry Mountain hunt in UT, the public land hunt in AZ, the Custer State Park hunt in SD, the Yellowstone hunt in WY/MT and the Alaska hunt, it doesn't take too long to find them. And they aren't too difficult to kill. I use a 450 Marlin when I want a bison in the freezer and it tips them over nicely.
I think the last one I shot was about 7 years ago and I always got them in WY since the price was good. If my memory is correct I gave about $650 for a big heifer cow and she boned out right at 420 lbs of meat. Price bison meat in the store and you'll see what a bargain that was.