This should be the way when we do the shopping, always choose the product which is the most suitable for you not based on other factors. If a supplier can offer me 15% discount by paying cash compare to 0% discount paying by AMEX, then I will cerntainly choose the cash method, why should I pay 15% extra to get those points which are only worth $5?
Agreed.
Although, I am the first to complain when my preferred option, AMEX, is not accepted or is surcharged I will always pay by another method to get a better price (not to avoid surcharges which motivate me to go elsewhere). I am not one that shops for points. Points are a bonus and if not kept that way, you could purchase all your rewards 10 times over with the savings you have missed out on.
However, how many businesses take the position of rewarding you for cash rather than penalizing you for using the payment method best suited to you the customer ?
Generally, if you shop around you can find an equivalent product or service, ask for a discount and get it and pay the way you want.