The license on the Bluray and DVDs that RedBox buys (Rental Licensed) typically require paying out royalties from the rental fee. As with all royalties, these are negotiated, but I have heard from people who ran their own DVD rental store fronts (when that was still a thing) that they could be as much as $5 per rental on.

Also the disk is usually a LOT more expensive (up to $100 for a new blockbuster release). DVD store fronts were already so low margin, it didn't take much disruption before they started to go under.