I’ll try to dig out the feature where I read this but although initially their viral videos did drive album sales (to the extent that they were one of the few bands on their label who were in the black), they actually make most of their income from corporate sponsorship deals (e.g. the one where they’re driving a car was sponsored by Chevy, there was another one sponsored by Range Rover and another one funded by Samsung). The products aren’t always in the video so some are more blatant than others.
It’s actually a kinda genius business model, but you can’t help wondering how much more successful they’d be if most of their songs weren’t rubbish.