....may I comment.
There are differences at NAPA, from store to store. Don't know exactly why but they do. In "My" part of the country the NAPA stores do not store a lot of the kinak knacks that Auto Zone and Advance like to hustle. Here NAPA is hustling the commercial business and doing a good job of it.
As an example of differences.....my nephew, a full time mechanic, has one account in his business name, and one account just in his "real name". Well I'll be darn, sometime his real name account gives us a price cheaper than the business name on the same product. He lives 20 miles from me but at times I can buy it from my commercial guy here in Boiling Springs, cheaper than he can!
I think prices, in my opinion, is based on what segment of the business they are after, in a particular location, and the competition.
I also know that just about ALL the parts houses has a bogus account, or a business account, that they can use to let their daily customers, who are not a business, but yet get great prices. I've been doing this for years! HOWEVER, it is predominantly through the COMMERCIAL guy who is usually at the back or off to the side.
My go to GIRL at Advance, who has handled parts for over 25 years, recently went to NAPA. Guess what, I still get great prices from her on "most" all things. Some not so much and she will tell me.
Accounts like "who nose garage" or "Sunset Repair" are just a couple. A commercial sales person likes to look out for their "favorite" customer so as long as you pay in cash they will bill it through that customer, which in turn shows the customer doing more business with them, and gets the shop a "silver, gold, or platinum discount... In my case, I know some owners at a couple nice garage's and they have gave me their personal OK to buy my stuff through them as long as I pay cash. Works for me in my little town.
It takes time, but if your going to do much work it PAYS to get to know your parts man, or woman, real good.
......oh, and it does not hurt to take them a biscuit from CFA once in a while, or take them a couple hot dogs!