I've never heard of any chain auto parts store selling a "pair of brake pads" as in for only one side.
I seriously get asked this question a lot. People, for some reason, think the stores only sell left or right brake pad sets. They're sold in a "set". That means they sell all the front or all the rear, not just some of the pads.
You're going to get all four pads or all four shoes. I doubt you can even buy just one or two...
Oh, and usually they're going to offer several different levels of brake pads or shoes.
For example, for Autozone it's:
Valucraft (cheapest)
Duralast (mid)
Duralast Gold (upper)
Duralast C-Max (these are always supposed to be made of the same material the OEM ones are, plus they come with brake lube and the hardware included and rubber nitrile shims)
I would never, ever use Valucraft brake pads (or probably any other part by them...). They're crap. I even found a set split almost in half (I check every brake pad I sell before I sell it). The batteries die really easily tool.
Valucraft brake pads are usually about $15. Duralast are about $25. Duralast Gold are about $35-40. Duralast C-Max are about $50-60.