I'd pay for any gal that is pretty like her (especially with those eyes and my cock in her mouth) and who would happily wear or show off my load (the deal maker).
For me, it's like going off the beaten path of spinners and centrefold bunnies - sorta like excitement from doing something out of the ordinary, fresh, new or against conventional wisdom - especially with BBWs.
I've also found that whether or not it's play for pay, bigger girls try harder to make you happy, and sometimes even seem to enjoy it better.
Nevertheless, it's not my main fancy.