Beats was very smart, just send every ball players a pair and when people see them wearing them in pre and post games, they automatically want it. Dre's name being on it doesn't hurt either, it makes those ball players more eager to wear them too w/o any pay. It's the most basic of all marketing though and it has been going on in Hollywood for a long time, in those Oscars, Grammy, etc.. they hand out gift bags chuck full of free stuff and when they are seen wearing it, free advertising. Kanye himself has like 2 garage full of just free stuff he doesn't even use. Targeting nba, nfl, mlb, etc... players are smart because they already wear headphones when traveling and they are always photographed so it goes hand in hand.
Beats doesn't even need to make the best product, I know people always talk crap about Beats but unless you are an audiophile, sound quality isn't going to make much of a difference. And their quality is pretty good, I have been heavily using the powerbeats ear clip-ons for maybe two years now, which includes 2-3 miles runs daily and it's still going strong.
Supreme seems to be on the same marketing gimmick but I think they also sell out because of hype and limited products, as in they do not have every Target or Macys carry their products and they do not make 100 pieces for each size of shirts for example? I could be wrong but that's how Balenciaga is selling out their sneakers right when it hits a restock online, they just have one to two pairs per size so they sell out quick and people wants it more because it's more difficult to get.