Last time I checked, there was no discount for using bitcoin. For me personally, there was no incentive to use bitcoin. As a bitcoin enthusiast, however, I always check Overstock and Newegg first when making a purchase...and I use $US. Why should I spend BTC which I value when I have USD to dump on them? Why should I spend the exchange fees to purchase BTC and send it to them?
The incentive shouldn't be to get a discount but to support both bitcoin and merchants. Why spend fiat? Don't buy from exchanges if you don't want to pay any fees.
please do some research, reread my post, then edit or delete yours.