Presumably what you're talking about is the fact that the summed "exits" are less than the input investments. But it's not a steady state environment. Obviously exits are going to lag the investments by several years, and the rate of investment hasn't been constant -- it's been increasing steadily for several years itself. So you wouldn't expect to see a net profit.

The real question, of course, is whether we should expect to see a net profit across the incubator/accelerator world at some point in the future, or if we're indeed in the bubble some of us think we are...