I don't think those prices are way off, I seem to recall paying less in Texas, but then it is Texas. In Cali, I think that's probably about what I paid. But I go so infrequently that I don't quite know (and when I show up, I don't really care, I'll pretty much pay whatever) - I'm sure others will know right away if those are good prices.
If you've never shot a .50 cal revolver before - that is certainly an experience
I don't think I'd do it again, but definitely worth doing it once just for fun. Forget accuracy (and make sure you grip down low too - I think there was a mythbusters on this and it was actually proven that if you put your thumb by the cycle you can get injured from the blowback). I shot the .50 in LA - now that had a fricking kick, maybe partially because I gripped down lower than I normally would. I got my wife to videotape that experience - its good, if I go shopping with her, she'll come to the range with me - pretty cool