The benefit received from paying less for a good than the maximum amount that the person is willing to pay for it. Thus, if a person is willing to pay up to $3 for something, but the market price is $1, then the net economic benefit for that item is $2.
Her bias is known as "the outgroup homogeneity effect".
Outgroup homogeneity is the inclination for individuals to see ingroup individuals as more differing than outgroup individuals. The Outgroup Homogeneity Effect is the propensity to see an outgroup as homogenous, or as "all the same," while the ingroup is viewed as more heterogeneous or differed.
