The cost for aviation parts is way over priced due to product liability and certification costs which leaves little room for profit. OEM automotive and motorcycle parts have a 100% markup over dealer cost and there is generally a matrix added to that, aftermarket items have a 30~40% markup, your local A&P is lucky if he can average a 10% discount from retail. When I had my Motorcycle shop the labor rate was $60.00hr and my A&P was at $45.00hr (he's now at 60). I honestly don't see how an independent A&P\IA can afford to have a large inventory of parts on hand, I know I wouldn't if I was one. I assume a seasoned A&P has around $40k wrapped up in hand tools and at least that in specialized shop equipment so don't complain to loud, he has a lot invested in education, money and time keeping you from falling out of the sky. Short story, I had a Doctor bring in his 3-wheeler in for tires back in the early 80's, I told him lets go up front and check prices so I could give him a heads up on the work requested, he said he didnt need an estimate and to call him when it was ready, back then you could only get the tires from a dealer, roughly $100.00 bucks a pop, so 3 tires plus labor & tax was pushing $400.00 on a 3-wheel that sold for grand when it was brand new. When the Doc came in to pick it up I slid the repair order across the counter as I gave him the total verbally, he stumbled and stuttered and said I'm a doctor and don't make that kind of money, which I replied neither did I when I was a doctor, will that be cash, check or credit card...