He acknowledges that it wasn't universally stolen: the income was approximately $2/hr. If it was universally stolen, the income would have been $0/hr. But what he was missing was that it was universally wanted, there was a demand for it. This means he didn't set a price that the market was willing or able to bear, and the market told him the price that it was willing to bear. One way to adjust prices in the face of piracy is to take the total income divided by the total number of users (this is an iterative process, because this might not be immediately measurable). Considering what people had to go through to obtain copies on the Altair (making copies of paper tapes), the price set ($500 for the standalone version according to http://en.wikipedia.org/wiki/Open_Letter_to_Hobbyists ; approx $1900 in 2009 dollars) was way too high considering the effort of copying. At some lower price point, the effort of copying is too much for the price set.
While it's nice to be able set whatever price you want and think you're going to get it, that isn't the case. And banking on being able to sell at some arbitrary price is folly. Because you'd be in the same situation if the people DIDN'T even bother to copy it in the first place, the only difference is that you get to complain that people are using it without paying.
Charging $500 for something that is in high demand and is easily copyable, well, that's a huge mistake. The market is telling you there is interest, but you're not meeting the buyers, so they subvert you. And while it's unfortunate that all this effort and money and time was expended up front and now the bill comes due for, setting the wrong price, which discourages sales and encourages piracy, is bad market research. And Microsoft changed in that regard too, for a long time now Microsoft has been known for its marketing juggernaut.