This is the price for a single cell or battery of this brand. This is simply the total price divided by the number of cells. Of course, it is more cost-efficient to buy batteries in bulk, as you get a considerable discount on the price per cell this way.
Please note, that in the english version of the website, the prices are in Euro; the original prices in Bulgaria are in Bulgarian Lev, BGN. So, if a price sticker is seen on some of the photos, it marks the BGN price, and this might be the reason for the discrepancy, in case you're wondering :)