(1) "how can they be making any money when everything's twice as expensive as it is online?"
(2) "how can they not be making any money when the shops are always packed?"
One possibility - no-one is visiting HMV to buy any more, just to browse or socialise and see what they'll order online later. So the shops are always packed but no money is changing hands...sure, it's possible. Anecdotally, plenty of people increasingly treat the high street as an opportunity to look for things they'll buy later, more cheaply, online.
(Photo from Kwanyastsw on Wikimedia Commons)