This is the price of the pictured battery package; with AA/AAA cells, this is usually a four-pack, except where the store only sells larger packages. Usually, there are also larger and more cost-effective packages - in which case, this is noted on the details page for the respective battery brand.
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 :)