The pay scale of the USMC is the same as the pay scale for all of the United State's military services - for example, a private first class who has been a Marine for two years is paid the same as a private first class in the U.S. Army who has two years of service. (Either might get extra pay for such things as being in a war zone, such as Iraq, of course.)
You can find the official military pay tables here, at the Defense Finance Accounting Service website.
Keep in mind that housing and food is provided at no charge to enlisted soldiers, and, when this isn't possible, they get tax-free payments ("allowances") instead. Officers get either military housing or a tax-free housing allowance.
And there are other benefits, such as G.I. Bill payments for education; any military recruiter (which I'm not) will be happy to discuss these.