I sell things online on eBay. eBay has a function that allows the seller to send a discount as an offer to an interested buyer. If I was in the middle of sending the buyer the discount, but he bought it for full price before the offer could be sent/completed am I required to refund the buyer for the amount of the would be discount or can I keep the full payment?
There is no need or you to give the customer the discount. Although it is very considerate and extremely honest of you to ask the question, you are not obligated to give the person the discount. There was an amora that did this, however that was considered an extremely pious act, and it isn’t an obligation.
Seiltis 36, Makkos 24a