Financial infidelity surely is a new term to me, as I havent felt that yet. But what you mentioned that the discount money is surely a trick that cost some extra money going out of pocket in the act of buying.

It is way common for people everywhere, when I went to the market to buy a furniture, the offer was like " buy it with 25% less ". Also with installation on.

Which adds that - temptation was there to buy it, if the price was high, I wouldn’t be buying it anyway.