The money thing was probably a) a novelty to him, having grown up at least temporarily in a less-than-fortunate circumstance, partying it up with a bunch of easily-earned cash (especially as a 17-18-19 year old) was obviously a thrill, and b) sort of feeling like at least something good came out of all the horror. He's too sharp of a guy to be content with just that though, I think eventually he'd have grown out of all that though, and needed something more substantial. Jake was basically holding the peace together and training up a new breed of high-tech special forces, Cassie's keeping the Hork-Bajir from being wiped out by extremist humans, Ax is running a friggin' Dome Ship and its battle-group. Pretty sure Marco's not going to stay teen-idol butler-teasing womanizer-extraordinaire forever.