Tire prices from Good Sam RS

Back in September, I had the misfortune of blowing an inside dual on my motorhome south of Salt Lake City in Utah. Had some damage to the storage box behind that dual, but not bad enough to be towed, so called GS to have a tire brought out. Knowing that the other tire was due to be replaced when we got home, told them to bring 2 so they would be matched up for another 500 miles to home. Not complaining about the 4 hour wait, not complaining about the tire companies service. I do have an issue with the person I dealt with on the tires when I told her I would pay the tire service company cash when they installed the tires, but they insisted to charge my credit card over the phone, with the price quoted from Good Sams National Contract with Goodyear seeming extremely high at the time, but I was a captive audience at the time. They asked me for my e-mail address at the time, and I requested a snail mail receipt. A week after I got home, I took my motorhome to the local Goodyear Dealer, a company my former employer has dealt with for years, with a yearly contract that we always joked was the highest in town. Expecting to pay dearly, but wanting to purchase the same brand of tires I bought in Utah, I bit the bullet, and had 2 more installed. Now here's the kicker. The price difference from the 2 purchased in Utah under GS National Contract, and a week later the 2 purchased at the highest priced tire store in our town was over 400 dollars cheaper! The folks at our local store were scratching their heads as to how that could be. So, taking in to account that the road service fee is paid by GS, there was no tire balance done on the side of the road, but was performed at an additional fee at our local store, plus all the neat California tire fees we get to pay, how can tires purchased under a National Contract be so much higher? Somebody, somewhere, I think, is taking advantage of one when they are indisposed and at the whim of the system. As an aside, 40 days have passed, I've made 2 phone calls requesting my receipt for the tires purchased through GS, and still no response.