At Common Cycle in Ann Arbor, Michigan, I saved up the discarded tires for the summer season and then dropped them off at the recycling center.  There was a fee per car-tire unit, so the staff eyeballed my stack and estimated a conversion to car tires, and I paid that amount for the disposal.  It was not wildly expensive but I imagine it would add up over time, especially if you have a high volume.

Andrew