I'm not a statistician but I would guess gun sales track with people's notions of how steady their disposable income is or will be, whether accurate or not.
Guns are a niche consumer product with a limited market too, so I'd expect incentives to catch up to slumping sales faster than they would with other goods. Items with extraordinary markups to begin with, get "discounted" all the time. That's why furniture is on sale for every holiday. Guns, from what I've always heard, are low margin so there's probably not much room to cut deals unless the seller is a volume dealer.