Just keep this in mind, he has a shop with overhead, insurance, experience, and time invested in it. He has to make money some how. If you support your local business then he can stay there and continue to service your area. How much time does he have invested in figuring out what parts and part numbers you need for your exact combination? How much is his knowledge worth? Did you know exactly what you needed before you went to him? Are the parts you are getting off ebay new or used? what about his parts? What is the quality difference? If a part is wrong or doesn't work, what kind of internet warranty do you have? If he gets the parts and they don't work as he claims the odds are he will take care of it.
I'm not going off on you but I want to understand that as a business owner, we have to waste a ton of time looking up parts for customers based off of our own experience then listen to them complain about the price. The $300 tuning charge is a bargain for sure so he has to make money somewhere and the markup on performance parts is less than half of standard replacement parts. I guess we could just buy everything on ebay then wonder why all of our shops have closed down...