People get so excited they don’t even look deeper at what’s real.
The salesperson encourages people to dream about the product, then people in their greed don’t look at what’s really there.
As a result it’s only possible to cheat a greedy person, as an person won’t get so excited by greed that they don’t look properly into it.
A greedy person would also be so greedy that they justified themselves that is real, even when it isn’t.