Since there is no correlation, all Amazon will be trying to do is move as many
fanfic sales transactions as possible, quite irrespective of whether
fanfic A is better (or
worse) than
fanfic B.
In many ways, Kindle Worlds looks like you get the
worst of both worlds — lose the community and feedback and audience and the chance to write exactly what you want without oversight or marketing concerns that you have when you write
fanfic, but totally lose rights to your work (so you don't even have the grey - area maybe - fair - use - maybe - not rights of a
fanfic writer right now) and get far, far less money than you would trying to sell original works or public domain fic.