I've known people who work at Best Buy and they get their products substantially cheaper, just as the online retailers do. There is some level of bake in for storing it at the store... but not really much different from sitting in an amazon warehouse for instance, most best buys have large warehouses in the back you'd never be aware of. Many people aren't aware of the price matching nor take advantage of it, they also sometimes will "confirm" the price match, so you can't really fake them out. And you end up browsing whilst they do the price match + grab the product from the back.

Long term sustainable simply because they've already baked it in and it's less widely known amongst the typical consumer and its honestly kind of a hassle, people pay for convenience.