That expensive painting someone bought a couple of years ago is now worth 80 percent less. Typically, art, like other commodities is purchased at its peak price, a sign of economic downturn is a drop in price -- the larger the drop, the worse people expect the future economy to be.
http://www.bloomberg.com/news/...urs-for-about-20-000
Whether, copper, gold or pork bellies, commodities are not a good long term investment. At least, with pork bellies, one has a good supply of bacon.