For once, I agree with Chubulor. (Don't get used to it.) PhD's in highly valued areas such as the sciences, engineering, finance, etc. almost always receive full funding (other than textbooks) for graduate school. The line in these areas is "If you have to pay, you shouldn't go." because the department doesn't think you're going to graduate, otherwise they would give you money. These are the same PhD's that pay very well after graduation because the market values their output. There is a reason the number of PhD's teaching in the US is increasing foreign, because our universities pay better.