The problem with shop level primer sales is there is no "secret source" where they can get primers substantially cheaper than normal people. Compare this to other industries like retail clothing, bicycles, jewelry, etc. where you will not get near a "dealer price list" unless you are in the business. (And no, the rap sheet is not the "dealer price list" for diamonds, despite what it claims).
Back before the shortage, I checked some prices that a large FFL would have to pay for primers in MA. The prices were the same as you get in the valley, with the only "shop deal" being you could get them as part of delivery directly from the distributor (as part of a larger order of guns, accessories, etc. - normal retail stuff) without a hazmat surcharge. A shop would literally lose money selling them to at Valley pricing.
Back at the first great primer shortage, I found one shop that had SRP (that I use in 40S&W and 38Super). Word of the shortage had reached NES but was not yet common knowledge (that one seemed to spread from west to east). I remember telling the clerk "I'll take the WIN SRP". When he asked how many, I said something like "Did I mention a quantity? I meant all of them". Took care of a few friends at cost.
This is quite unlike other non-gun stuff in shops - those holsters, range bags, cleaning kits, etc. all have healthy double digit markups from wholesale/distributor to retail, and are not individually bought in quantities sufficient to motivate online ordering in many cases. Plus, unlike primers, you can't get them for the same price a storefront dealer can. Similar situation for powder.
In the days of readily available primers, the solution was "just don't stock primers". Now that the shortage is here, the dealers are willing to pay hefty prices because the market will support a 50% markup on $80 bricks when previously they would be lucky to get 15% or so on 40$ bricks.