Just to add to your point about marketing being important to assess something's value, take black pearls. They used to be worthless and producers couldn't sell

Just to add to your point about marketing being important to assess something's value, take black pearls. They used to be worthless and producers couldn't sell them at bargain prices. But then one jeweler placed them next to sapphires and other precious gems on display and they became a quite expensive item. I'll add a link to this story if I can dig one up.