I've tried to give blood in the past, but I nearly always have a sinus infection (to be descriptive, yellow mucus) so I can't. The blood drive in Clemson is always in the fall, when I'm usually sick until the weather gets warmer.
As for the "discount", it doesn't sound like much of one. Not worth the drive, at least. I think most of my purchases (on ammo and guns) will be at the Gun Shop in Walhalla, SC. $30 to $40 cheaper on pistols, even hundreds less on older rifles - like an M1 Carbine for $500, the Swedish M96 my friend got for $200, and the Mauser 98 I got for $100. The sticker price is for credit, I paid with debit and it knocked $10 off the price. So if you live in SC, I'd think about that place.
As for the event, it sounds like a novel idea, perhaps encouraging people to give blood may interest them in guns (hell, I'm always interested in BBQ). However, if the prices are high, this might turn some people off - so it may do more harm than good.