as someone who runs an LGS, you've got it completely backwards bossman. Market value isnt determined by stores, it is quite literally "how high can the price of the thing go before people stop buying them. Stores selling at market arent making the price, they're quite literally responding to what the boxes are already selling for. I can absolutely guarantee that if people werent buying at double, triple, quadruple what msrp is, they wouldnt be selling it at that price point. You'd have to be massively inept to price cards at prices nobody is willing to buy at.
You're also just completely wrong here. LGS arent the only people on TCGplayer, if every single brick and mortar store was strictly required to comply with MSRP, nothing would change. Scalpers would just buy from the store and flip the product for a profit online, like they literally already do now. Where do you think scalpers even get product from if not from places selling at msrp?