The threshold effect refers to the phenomenon of putting forward a small request before putting forward a larger request, so as to increase the possibility of others accepting a larger request.
The statement 'Smart merchants often set the price far more than the actual due price when selling goods, and then let customers accept a relatively low price when bargaining. In fact, this low price is still higher than the due price of goods, but customers often enjoy it' belongs to the threshold effect according to the above definition.