The valley of death, as I mentioned in my intro remarks, is the period in which you will invest a lot of money developing a technology without the assurance that it will sell. The valley of death extends to the early commercialization period, because when you have a highly technological, highly innovative solution, there is a fair chance that your first clients will get a prototype-level solution and it will probably cost you three or four times, 10 times or 100 times more to produce that first prototype than you can actually get from the sale.
The more you sell, the more your balance sheet goes into the red. That's the valley of death.