Floyd Mayweather Charging $999 For Cameo Vids, 'Most Expensive Celeb' On Site

Want a personalized shout-out from Floyd Mayweather?? Hope you've got an extra GRAND laying around -- 'cause TBE is charging $999 for Cameo vids!!! Floyd joined the popular site this week ... and in true Money Mayweather style, he claims he's now…