Like most people know, caviar is an expensive food made from salt-cured fish eggs, specifically eggs from the Sturgeon family. Currently it costs around $2500/lb. What a lot of people don't know is that caviar wasn't always expensive or considered a delicacy.
It wasn't until after 1900 that this became the case. Before that, caviar was so abundant in the U.S. and Canada that we used to actually be the major suppliers to Europe. In fact, caviar used to be so cheap that it would sometimes be served in American saloons, often for free. They served it for the same reason that peanuts are sometimes given out for free at bars now, ie. that the salty taste would make people drink more.
After 1900 it gradually got more expensive, and the price went way up in the 1960s. That happened basically because overfishing and polluton in the Caspian Sea (the world's main source of wild sturgeon).