Floyd Mayweather -- SORRY JAY Z ... Not Going to Your Party

He can DEFINITELY afford tickets, but Floyd Mayweather says he WON'T be hitting up Jay Z's post-fight mega-party in Vegas -- there's another place he's already committed to be.
TMZ Sports spoke with Money at his media day workout at his gym near the Las Vegas strip Tuesday night ... when it was pointed out all of the post-fight party options he has... Chris Brown, Nicki Minaj, Snoop, Jay, etc. So he'll most likely be going to one of those.
By the way, VIP packages for Jay's shindig are on sale for up to $50k!!! Insane, but a drop in the bucket for Floyd.