Beware of Mr. Appliance (or other repair places)

I know you can't see me as I write this, but I have steam coming out of my ears (also the word "Sucker" written across my forehead, apparently). I was having trouble with my Kitchenaid Superba gas oven. I called Kitchenaid's service number, and after asking me several questions about it, they said I needed to contact a service company to come look at it. They gave me a number for Mr. Appliance located in Jonesboro, I think. I called and a guy came the next day to look at it. He was nice and covered his shoes before he came in, which I did appreciate. He ended up calling Kitchenaid (or Whirlpool) as he was looking at it and the final analysis was that it wasn't lighting and I needed a new gas valve and ignitor. I had two choices, I could either pay $55 for the service call if I chose not to have repairs made, or pay for the parts and labor, and he would come fix it when the parts came in. This is where I made my mistake. I went ahead and paid for the parts/labor. This was last Wed. or Thurs. For some reason today, I decided to get online and check out the prices for those parts. I almost wish I hadn't. I know people have to make money, and I figured the parts I found online would cost a little less, but was I ever surprised. The gas valve, for which I was charged $150.08, could be aquired for $97.18. The ignitor, for which I was charged $116.24, could be aquired on the same website as the other part for $66.10. I was thinking they would be at most maybe $20 more. I called Mr. Appliance and asked why couldn't I order the parts and then pay him for labor. I was told they order from a distributor and can't send parts back once they're ordered (which seems suspicious to me). I got no satisfactory answer to my questions about why the parts were so much more expensive, so I called Kitchenaid. Of course, I was told they have other service recommendations online, and that Mr. Appliance is an independent service provider, etc. etc. etc. Since we won't be able to get it fixed until after next week, I'll not do anything right now. But, Mr. Appliance will certainly hear from me before they come out to do any work on my oven. I guess I'll have to do my dad's "May I please speak with your supervisor" routine until I (hopefully) talk to someone who will answer my questions.
The moral of the story is this: Buy your own parts, or at least get some other quotes. Also, do not pay for service that has not occurred yet. Had I to do it over again, I would've looked up those parts online (and made the service guy wait while I did it). I also would not have paid for the labor to put them in until he actually put them in. So, learn from my mistakes People.
I will update this when I have resolved this issue. I hope it doesn't take too long!