This seems to be a nice project todo in your spare time. Buying it? No thanks, I don't see how this will benefit me. Selling these for 500$+ ? You must be joking.
Questions like this seem a bit pointless in my opinion. I mean sure, a lot of people get to answer with their insights and opinions on the said language/tool, but in the end isn't everything you learn going to benefit you and make you a better programmer? So asking if something is worth learning will probably always get a positive answer because the more you know the better (even if you don't get to use that specific tool you ask about).