I think it would take an awful lot of java moss to weigh a lb.(unless they weigh the water too). It may be that it's not all that over-priced if they just take a handful out and set it on a scale, then bag it for you with some water. Surely they want to sell the stuff, not just have it sitting in their tanks tying up their money. Go back and check it out, ask them specifically how much a handful sized portion would cost you, don't worry about a "per lb." price. If it's too much, you can always say "no thanks".
I agree, Java moss is great stuff, I have it in several of my tanks. Get some if you can!
Anybody seen the java moss "balls"? (I know, I'm setting myself up here) They look different than the standard Java moss, grow, or are grown, in a round ball shape. I wasn't particularly impressed by it, but it was something different that might look really good in the right tank setting.