I don't have a dealership but have been in / around the auto repair business for nearly 40 years.

I'm all for value shopping and yes some parts are more at a dealer than aftermarket ( especially older stuff that does not go to dealer for service. )

When I needed a wiper blade for my 97 C280 , they were $ 25 for Anco at the auto parts and didn't fit properly, it was $ 18 at the dealer and fits!

When I got my 97 SL320, I replaced _all_ coolant hoses ( except for the molded ones feeding the heated windshield, being a summer car I bypassed that ) dealer pricing was inline with aftermarket of dubious quality and, one sub $ 20 hose was sent next day air from Germany _FOR NO ADDITIONAL COST, try that from the cut rate or even good quality parts sellers.

Opening a car dealer store, this way you can sell everything at low prices.

Yes, please open your wholesale business to retail, this way the low end Wallmart shoppers can call you a stealer. . ..If you have never run a retail business, you have no idea what you are in for.. . It is even more difficult being in the auto repair business where customers ( like your self ) are unhappy that they have to spend $ on car repairs and take it out on everyone involved.