if you know a seller well they are normally open to doing a nice deal for you. I can normally get ~10% off on new prices with some shops and they do that since I keep returning to their shop for more purchases.
what that tells me is that there is some kind of back handed fixing (whether its via. suppliers or whatever) as mentioned above and there is some leeway for them to move prices around for their regulars without advertising it widely.
I feel this one of the reasons why a lot of grey seller have gained traction in UK and also in lot of places in EU. Almost like slowly digging their own graves.
also what really gets me is you pay more for being an early adopter. You get to pay more for buying first and making their new products a success. this is one thing I do like about kickstarter or crowdfunded projects where early adopters are thanked with nice discounts for making their product a success,