"The greater fool theory states that the price of an object is determined not by its intrinsic value, but rather by irrational beliefs and expectations of market participants.[1] A price can be justified by a rational buyer under the belief that another party is willing to pay an even higher price.[2][3][4] In other words, one may pay a price that seems "foolishly" high because one may rationally have the expectation that the item can be resold to a "greater fool" later."

:-)