Unfortunately, I know the repair part pricing game as I set the repair parts price for a major appliance manufacturer. President would come to my boss and I and ask "Can you find an extra $300,000 this quarter?" My response: "Not a problem, sir." And I would. Minimum markup is usually 100%. Then the parts distributor marks it up, then the repair shop adds their % so you get the crazy pricing. Add in shop labor rate... I used to love the stainless steel appliance fad. My repair part cost for a stainless steel refrigerator door was about $5-$10 more for stainless than the painted ones. Yet I could sell it for at least $100 more because of it being stainless and people wouldn't even blink.
I do my own repairs whenever possible for my business. Replace a potentially bad pneumatic valve? $400 from the CNC manufacturer. $62 from the importer of the valve to the US. Fixed the overhead sander yesterday for $3 in parts from Ace hardware. Broke a fitting on my 20 year old edgebander. Manufacturer said they don't even make that part anymore. Scheitz! So I drew up the whole pneumatic manifold and went shopping at the Parker store. $140 in parts later and I'm up and running.
Find a good reputable shop and develop a relationship with them. They will give you a break when needed and watch your back. My business neighbor is a tire shop. He gets me tires at cost plus a small fee to cover his labor. In exchange, I let his guys park in my lot when the snow flies and people suddenly realize they need new tires.