At my shop I normally charge $8.00 to stud a tire I sell, $12.00 to stud a carry in. WILL NOT STUD a tire that's been on the ground (no, not even across the street and back) because the little holes to install studs will pick up small gravel. These small stones will ocassionally break the "fingers" of the stud gun. To replace fingers, one must buy a complete rebuild kit,somewhere over $100.00 last time I checked. You, or the next Joe Bloe aren't willing to ante-up for broken parts, so, I'm not willing to take that chance for the pittance involved. New tire customers should'nt have to pay more to cover my losses from attempting to stud used tires.
Bob