To PhD or not to PhD

The Economist ponders the rewards (or sometimes lack thereof) of the infamous doctoral degree. It is a question I have often pondered myself, having completed the requisite undergraduate study and being encouraged by my honours supervisor to consider a PhD. I have some friends who are currently studying towards this, and they seem to be doing just fine. I am aware that there is a lot of work involved (which I would be willing to do), but something I am still grappling with is: what would I get out of it?