It is $10, unless you get an up sell at the checkout. Then it is doubled.
If your ever in one of the stores, look for bags of M&M's that are mismatched colors (not a normal color blend) that are wrapped up in the clear cellophane in one pound bags on the counter of the checkout. They are sold at my location for $3 a bag. It was the only thing in the store I picked up and looked at that was not priced. I had my little $10 worth of M&M's from the wall and then when I was showing interest in these unusual colored mixes, I got my up sell and grabbed three of them for the real score.
I am thinking that they may be the candies that people pull from the wall and fill into bags and then abandon at the checkout or elsewhere in the store. When I was at the wall, someone handed back a big bag that they changed their mind on purchasing. The assortments were mostly one color, like buying OOPS paint at Home Depot. I got mostly dark blue with some light blue mixed in. They were all peanut M&M's.