It's not really about the money, though. The number of qualified, published academics in CS is just not high enough to meet new academic demands. I'm currently a student at an Ivy League school with an extremely reputable CS department, and we just hired 3 new professors who were considered big wins for the department (we have also seen a quadrupling of CS majors in the last 4 years). The thing is, we sent out something like 12 offers. Schools across the country are trying to scale their CS departments as elastically as they can (Yale, for instance, just launched an initiative), but the number of qualified professors is relatively inelastic. Of course, not all teaching jobs require a PhD (intro classes and applications classes, for example), but there are so many other more theoretical classes that do require an experienced professor.