I've been reading through Morrison's JLA run recently and am currently on the second Deluxe hardcover. I went online to do a little background research into the Rock of Ages storyline and came across some copies for sale.
There's one copy available on Amazon for $669. Other places have it available anywhere from $99 (ebay) to $282 (Barnes & Noble).
I mean, it's pretty good... but not that good. Even if it's a scarcity thing, there's a paperback version that can be had for less than 20 bucks...