I think we'd be naive to assume money is not a strong motivator in entrepreneurship. It may even be a primary motivator for some, though few would admit it. That said, it can't be the only motivator. Not because that's morally repugnant or anything (I don't make moral judgments here), but because it's not a realistic or sustainable source of motivation.

If all you want to do is make money, then you would be foolish to pursue entrepreneurship. Your expected return on starting a company is significantly less than your expected return on doing something like investment banking. Sure, you might strike it super-rich and become a billionaire through entrepreneurship. More likely than not, that ain't gonna happen. Conversely, you can almost guarantee yourself a fortune in the millions to tens of millions (and maybe even hundreds of millions) if you bust your ass in high finance and are great at it.

In summation: How many of us want to get rich? Probably most of us. How many are doing this solely to get rich? Only the silly ones.