We can all name a few of them. Those ones who not only show that the main reason for their performing is the paycheck, but they put it in their songs/names! The ones who make money the focus of most of their songs. The Lil Waynes and the like.
I remember when people used to look down on people like these, calling them "sell-outs", but now the younger people are seeing this in a different light.
Look at any group of rappers/artists these days, listen to their songs and you will easily be able to tell who they are. You get the groups who have names like YMCMB (Young Money Cash Money Billionaire) and Cash Money Heroes. Their music might appeal to their listeners but I really don't think this is the message to send to the younger potential artists, to "do it for the cash".
This is not restricted to Hip-Hop and Rap though. There are many rock bands, famous or otherwise, that couldn't give a damn about their enjoyment - or the enjoyment of the fans for that matter! They go out there, play their set, and feel their wallets get fatter. It's disappointing.
The need for money is understandable though, without being paid most bands/singers would go broke very quickly and need the money to continue their passion for music. There is also the goal for most bands/singers to become rich and famous. That's fine as well (I know that's where I wanna be one day). But to treat music like a job where you "work" for your pay and treat your music like a source of income is just plain embarrassing.
In short, choose music as a career, not a job! Enjoy your fame if you get there! And don't let money become your focus!