I can think of several reasons to offer a discount for bitcoin. Added privacy, exchanging usd for kyc free Bitcoin seems to come at about a 2% cost. The cost to exchange USD for Bitcoin also seems to come at a cost of about 2% on cashapp. The question is what is the cost of those USD to the business at that moment... If the business is going to convert it bitcoin anyways (as in they want Bitcoin) there is likely a cost to get it to bitcoin, therefore it makes sense to offer the goods/service at a discount in order to acquire the Bitcoin (potentially kyc free)