Flexible Foam Aquarium Backgrounds

I had never seen those, but one of the LFS in my area is now carrying the foam rock for saltwater tanks. The owner is trying to sell me on how cool they are suppossed to be, and how they are rockscapping all these tanks with these fake rocks, but I just cant grasp the concept of it. They do look kind of neat, as they have automatic coraline algae color, I just could not imagine placing that in my tank. First of all, I have no idea what they are charging, but I saw price somewhere on some website, and they are outrageously expensive. Second, I wonder how it would hold up and look a couple years (or even months) down the line. And I just cant see how it could be as beneficial as live rock
I think I will stick with the "natural" forms of rock and decoration for my tank. I do have to admit, I did wind up breaking down and buying a couple of fake pieces of coral to place it in my FOWLR tank before it crashed again, but I was not overly impressed with that even and do not think I will be moving it over to the new tank