The money comes from all the silly money being poured into tokens and anything that looks like an interesting cryptocurrency... in this crazy world, it's actually possible to create your own currency out of thin air, print as many coins as you like and watch investors literally chuck money at it because it just keeps going up... at some point everyone is going to catch on that throwing money into a fire probably isn't the smartest thing to do and the steemit rewards will dry up pretty quick (will be pretty minor compared to everything else happening at that time)... welcome to the cryptobubble :)