some of the most renowned (and expensive) pieces of art on the planet are made of nothing more than a few ounces of paint schlepped onto a piece of canvas, sometimes decades if not centuries ago.
so, art doesnt have inherent value simply because of what its made of. you also cant eat art, or use it for shelter, or drive it to work, yet there are still people out there, that will and do, pay more for it than they would for groceries, a car, and their house, combined.
'perceived value' is a very powerful thing.
that said, the collector markets are very similar to the service and entertainment markets, in that they are the first to suffer and the last to recover during economic struggles.