Hard to say if they're too expensive right now. Looks like they're in the range of $200-$500 for sizes in the range of 60-200gig.
I can easily squeeze my entire webserver on to a 64 gig hard drive. And that price range isn't outside the realm of what I'd pay for a decent scsi drive already.
In a couple of years I'm sure they'll be huge and dirt cheap, but they seem to be in the affordable range already.