As a note, a friend of mine's father owned a gas station in upstate (real upstate) New York for years. His exchange rate for Canadian money was always 2 CAD to 1 USD. When people asked if he took CAD he said yes and informed them of the exchange rate. People would get angry and drive off, angry and still pay it or shrug and pay it. His dad saved all the Canadian money and when the exchange rate got most favorable would cash it in. They took all their
Disneyland and other vacations during the off season using that money.
It's smart business, not a scam, to set a flat exchange rate. If the buyer doesn't like the exchange rate they can shop elsewhere or convert their money.