Justin Timberlake & Ben Affleck -- FULL HOUSE In Vegas Casino

Justin Timberlake and Ben Affleck ... more enticing than money.

Take a look at the pic on the top... the casino floor at Planet Hollywood Wednesday.

Now take a look at the pic on the bottom ... snapped 2 minutes later.

The cause of the cluster -- Ben Affleck and Justin Timberlake, who were there for the premiere of their gambling flick, "Runner, Runner."