Ever try to mount a low profile tire before? Just cause its a stock mustang size doesn't mean it aint a bitch to mount. I see that extra charge everywhere and its a huge pain in the ass to mount a low profile tire without the accessory on the tire machine to aid the tire to stay in the drop center. I did a set of 255/40's and 275/40s many times and each time was a huge pain in the ass to not fudge the rim up, regardless, that shop sounds like a bunch of jerk offs anyway.