I don't know why a yasha goby would be better than any of the others... Although they seem to be quite trendy at the moment. I would only put a yasha in a nano or smallish tank, as it would become too likely to "lose" a yasha in a bigger tank (ie. the fish would be so small compared to the size of the tank that you may hardly ever catch a glimpse of it).
As for the price, it's all relative to how much you like it and how badly you want that particular goby. They run about $100 where I live when they are available. It definitely wouldn't be a fish I'd buy when I was new to the hobby, but now that I've been doing this for a couple of years and have more confidence in my abilities to have what I consider a successful tank, I would probably buy one for a 20 - 30 gallon tank if I had one set up.
