I have never seen a shop turn away labor to do anything, as that's where their profit is mainly. I have seen a shop charge more for tires brought in to mount, rather than bought from them. One shop here in Toledo, Homer's cycle, mounts the tire for FREE if you buy them at the shop... and he spin balances them too. He will order any tire you want if he doesn't already have them in stock. But, Jim is an Old School guy, and his business isn't dependent upon a small profit margin on tires, as he makes cables, cheap too, and re-spokes and trues wire wheels, very efficiently, and less than the incompetent mechanic does lol... I like them, too
Charlie