Like I understand music sales, although that can be over the top too.
But it's everything:
Movie sales
Phone sales
Video game sales
I'm starting to believe that y'all can't enjoy anything in life if it's not selling well. Next you won't be able to buy a toothbrush or a cup of coffee unless it has good sales.
Because its a measurement of success, not the only one but the most important to the Industry, Because its a business at the end of the day. Acclaim don't pay no bills
If your fave is flopping, then he'll/she'll get dropped by a record label. Success determines the longevity of your faves. Unless your faves settle for the indie scene then yall be probably luckier looking for them somewhere in your nearest drive thru selling mcdonalds fastfood than in an arena playing your most requested songs.
