Earlier quoted context omitted.
Why buy any drives from Amazon? I always buy from a specialty dealer. Where I am that's usually B&H.
Amazon has usually always been the cheapest option, especially compared to a specialty dealer. Costs add up when you're buying many drives.
Except, of course, for the dramatically cheaper drives you find from Amazon... which are definitely going to be used, defective, dropped, or fake. If you get them at all.
They all seem to be selling them for very close to what they pay Seagate (or WD or whoever) for them, and the competition between manufacturers probably means there's not a whole lot of room for that price to vary. And I think everything gets repriced pretty frequently whenever anybody's costs move. You can see the prices change at the same time at different sellers.
The reason I bought drives from Amazon was that I'd had Newegg delay delivery of an accepted order, and then cancel it for "lack of stock". A few days later Newegg had the same drives listed at a higher price. I assume that what they really meant was "lack of stock of the drives we bought cheaply".