They are worth what you are willing to pay for it. I don't think they are worth the $50, but I don't pay that much attention to them. If it's a buy it now I wouldn't, and if it's a shop then I know I wouldn't. They don't come up that much, but I thought I've seen the last couple go in the $20-30 range.
I have seen spikes in prices as well, and a lot of things went way up, then came back down. So if they have been going for $50 then maybe you could wait and it might come back down.
ETA: after looking I see that one just went for $90, didn't know any had gone for that price. I guess if it's worth it to you then go for it.