We who hang out on HN don't have a very diverse group of acquaintances. If we find someone to be an idiot, we probably don't waste too much time with him. So, we end up with a very biased view of the world. Given this, when we see a smarmy-looking site for an expensive parrot book, we laugh and think, "Who the hell would buy that?" The guy who's running the site was able to see how dumb most Americans (or at least English readers) are and picked a business accordingly.

Also, many of us would be embarrassed to admit that we were making our money this way, so we avoid even considering such activities.

So, what other information niches exist that would satisfy the needs of some small fraction of other 90-some percent? Yes, this question is arrogant, crass, and probably repugnant to many. However, it's the kind of question that Parrot Guy probably asked himself when he got started.