According to a quick calculation I made, in Istanbul (or anywhere in Turkey really), Classic Large Pizza is 6.22USD.

One pizza is 19.90TL, which is 9.94USD with current currency. But with 2-for-1 promotion, like you said it's +5TL, it's 24.90TL total, 12.45TL each, which makes 6.22USD.

I've checked both Dominos's website and Yemeksepeti's (the largest online food ordering website here) website.

(I was logged-in to both, I don't think so but, maybe there is a discount?)