In terms of financial payoff PHD is not the wisest choice, UNLESS you can invent something and market it. Faculty postions pay ok money and the workload is very light, but again the money is not there and tenured postions are very hard to come by.

The other bad thing is that with a PHD your job options shrink dramatically and your first job will probably be your only job.

Contrary to popular belief PhD's aren't more learned than non-PhD's. Non-PhDs are a lot more versed in emerging technologies and world affairs.