" To an Econ these two policies are identical. If the credit card price is $1.03 and the cash price is $1, it should not matter whether you call the three-cent difference a discount or a surcharge. Nevertheless, the credit card industry rightly had a strong preference for the discount. Many years later Kahneman and Tversky would call this distinction “framing,” but marketers already had a gut instinct that framing mattered. Paying a surcharge is out-of-pocket, whereas not receiving a discount is a “mere” opportunity cost. I called this phenomenon the “endowment effect” because, in economists’ lingo, the stuff you own is part of your endowment, and I had stumbled upon a finding that suggested people valued things that were already part of their endowment more highly than things that could be part of their endowment, that were available but not yet owned. "

― Richard H. Thaler , Misbehaving: The Making of Behavioral Economics