Some bands handle their own merchandising, in which case they get all the profit. But most bands that reach a certain level either hire a dedicated merch partne

Some bands handle their own merchandising, in which case they get all the profit. But most bands that reach a certain level either hire a dedicated merch partner or have their record label handle it, who take a certain cut of the profits. Using a merch partner/label can be useful, because they have better deals on bulk purchases on t-shirts and so on, which may or may not be worth it for the artists. The best way to support artists is still to attend their shows and buy some merch while you're there. Online shops, payment processors etc. all take a cut, so direct physical sales are best for the artist.