I'll tell you what has happened to me... when I buy multiples from the same buyer and go to pay with paypal, the discount is not figured in there automatically so I have to finagle it and then hope I did it right and the seller doesn't get pissed because I discounted it myself. Perhaps they were just not aware that the discount wasn't in the total due and/or were afraid to change the automatic amount due. (I mean, I have a 100% positive and I'm so worried a mis-communication will screw it up!)

Or not (I seem to be more wrong than right these days LOL)