There has to be strong demand (lots of potential buyers) for a rare item to sell for these stratospheric amounts. And, they have to be speculators. In other words, the prices for the rare item have to have a strong, constant track record of increasing. Buyers see this increase, like the line on a stock chart or the home sales in their neighborhood and make the fatal assumption; "It will always go up." So they buy even higher.
This is the definition of a bubble, and one day, perhaps, there are fewer buyers. That is because the "regular user" buyers drop out early, and eventually the "speculator" buyers do too. It has happened with early american art, vintage cars and guitars, etc. Those that bought high, are hosed.
There are a lot of lenses a lot rarer than this, but they are not worth a fraction. Because there are few speculators using them for "investments."
