Good walnut is worth the wonga, but there are many nondescript african woods also passed off as walnut, and there is a lot of variation in hardness. Good walnut shouldn't dent easily, but even if it does you can usually steam it out anyway.
American black walnut is quite popular nowadays, and is much much cheaper than english. I bought some for furniture making some years ago from a guy in oregon, and for anyone who's interested his website features mouthwatering piccies of black walnut in all sorts of shapes and sizes, including gunstocks.
http://www.gobywalnut.com/