I know this is likely to be viewed as off-topic or whatever, but... there are some really cute girls in grad school, especially the European ones. And they are past that whole annoying where's-the-party phase. You also get to learn a lot about a topic, from professors who think you have a brain and are worthy of conversation. So, I have to say, there are some wonderful intangible benefits to grad school. If I didn't travel randomly, I would totally enroll in a graduate studies program, merely for the enjoyable social/intellectual aspects. Some of you who are young and have cash-flow-positive startups should seriously consider it.

Not everything has to be computed in dollars/euros. Remember, there is a human aspect to your life that cannot be bought. You can't spend $15m to be 24 again, even if we DO find a way to live forever.