What you are talking about when you talk about those large salaries is something of a pipe dream for most people pursuing degrees. I too was lured into more education with high prospects but the truth is that it's really difficult to get in on the awesomeness. If you want to make a statement about long-term benefits you better talk about the average situation. Some PhD's do provide quite a bit more money on average, but a lot of PhD's (math, for example) provide only a marginal benefit over a Master's degree. I don't have the data in front of me but when I checked the situation for math, the difference in the mean was about 2-3 thousand dollars per year. If you take into account the financial opportunity costs of doing a PhD (things like low wages, tuition, loans), it will take you about 40-50 years AFTER finishing your degree to be on par, on average.