I am a programmer (hobbyist), and without that specific purpose or need, I ended knowing things in areas which I call "obscure areas" (since I don't know a better term). I mean, areas in which there aren't that many jobs, but there are almost no people working on them, or many having relevant knowledge at all. (E.g. Cobol programmers, people knowing machine language, kernel hackers, etc...)
These areas in some specific conditions, (such as the companies really needing them) result in jobs being paid very well. Much better than the average programmer.
The problem is that I tried to explain this concept to a friend (which has no hope in having a decent job; she wants to go further with design), and while she got my point, she couldn't have a single idea of such area in design.
I am not that wise talking about design, and ended pointing as a "maybe", to hybrid jobs (half of each area), like those at 3D animation/programming. Jobs where there aren't (as far as I know) many people working because of the limitation of most design people being bad at things such as programming, and most programming people being bad at things such as design.
I was hopping for you to give me an idea of hard areas inside design, where there are no big cost barriers to go in, even if there is a huge learning curve and requirements to have knowledge on it.