I had a service station job as teenager, mostly filling tanks, washing windows, but fixed a few flats using the plug method. I think we charged $4. But $30 in today’s prices seems pretty reasonable for a flat repair where they remove the tire from the rim and patch from the inside. Even in my teenage job I don’t think the owner would allow any sidewall repairs.
Mr Rick, makes good sense to be concerned about tire shops not treating your car well. My solution was to purchase inexpensive tire changing and bubble balance machines. Decision was pretty easy $$-wise, b/c I was in the process of replacing tires on both vehicles, 8 tires at $20 each replacement fee, -$160, compared to around $90 for both machines. Of course there’s a lot of work involved, so probably doesn’t make sense if you billed yourself for all that work. But for me, just another chance to have some fun in the shop.