Bear with me for this imperfect analogy: A have a few of friends who have written tech books. One of them kept doing it over the years. If the question is wether the money he has made from advances and royalties paid well, the answer is flatly "NO." The pay is quite small compared to the amount of time that has to be sunk into the project. But he keeps doing them. Why? The *real* benefit is that now he's an authority on the subject. This drastically increases his (and his consultancy's) value and has brought him many clients over the years. Being able to point to a working, published iPhone app is probably a lot more valuable to your career and/or business than whatever paltry sum you derive from direct revenue. Assuming there continues to be general demand for iPhone apps, at least. At least, that's one theory.

It's frankly made worse by the fact that (at least when I used complied languages, which was ages ago), it was hard to find a good reference. The old O'Reilly book was terrible. It was actually the K&P "The UNIX Programming Environment" that had the best intro to make.