Supply and demand...
Lots of horse operations here. No need to pay for manure here, ever. Some places without a loader are shovel-your-own. Others might want a couple of bucks for diesel but mostly they will contribute the tractor just to get the pile reduced. One guy offered to pay me if I hauled off upwards of 100 yds. He had a problem.
My truck holds 7 yds, and dumps. Enough to last my composting for a year. For a garden, pay attention to what is in the manure. My sources never know what might have been on the hay fed to the animals, but some herbicides will survive the trip through the animal and still be active. Not what you want in your garden. Dow is correct when it claims long life for the herbicide.
My manure always has de-wormer, routinely given to horses. Usually breaks down in under a year at the horse facility, but I never use manure that hasn't been further composted here. My garden's full of worms and I want to keep it that way. Waiting that long, the manure loses a lot of N, but with free (for the hauling) manure, I simply use more.