Diddy -- $250,000 Bet with Mark Wahlberg ... Over Mayweather vs. Pacquiao

Wanna see a couple of rich guys demonstrate their richness in ridiculous fashion?

Well, here's Diddy and Mark Wahlberg making a $250,000 bet on the Mayweather vs. Pacquiao fight ... like it ain't no thing.

Diddy's got Floyd. Mark's got PacMan.

The best part of the video is how casually these guys throw around their dough. In fact, the bet started at $100,000 ... but Mark wanted to know, "Why so little?"

For the record, the man who's wagering the MOST on the fight isn't even in the video ... it's 50 Cent -- who says he'll be plunking down $1.6 MILLION on Floyd.