When I lived in SC, I could have tires mounted and balanced for $12-$15 per wheel. Most places didn't care what wheel the tire came off of or went on to, the process is the same.
In VA, its closer to $25-$30 per tire for the same service. Quite a shock the first time I had new tires put on. $115 versus the $50 I used to pay. Now don't get me started on alignments which also cost twice as much up here. :-x