2-pack and 3-pack the same price

I have wanted to ask this since finding this board, it isn’t something I can EVER remember seeing in the US, but it is a not entirely uncommon situation here in Poland.

A product, (in my example, 1/2 liter cans of beer) is sold in a factory sealed, printed, shrink-wrap package of 4 cans for (the PLN equivelent of) $3.00 per pack, yet the same cans, when taken out of the packaging and rang up individually are just 50 cents each.
This is NOT a sale, but an all day, everyday price, and over here, opening a sealed package and taking just 1 or 2 items (to either save money or just beacuse you only need 1 or 2) is perfectly acceptable and completely common in all kinds of stores, big and small.

The first couple of times I saw this I was sure that it was a loophole, an oversight by the store, but it has been like this at one particular store for over a year now, with no end in sight.

(To make things easier to carry, and to make sure that the store doesn’t think I am trying to get away with something, I now take the intact 4 packs up to the cashier in the sealed wrapping, and then tear it off in front of the clerk who then rings the cans up individually and passes the savings on to me without blinking an eye.)

I have seen this with a few other products here, but have, never, ever seen the same situation in America.

Any ideas why they do this?

(Here in Krakow, like most civilized, God-fearing places, usually buying a multi-pack is a cheaper way to go, it is just that this seems like a no-brainer. Who wouldn’t open the 4 pack and save 33% instantly, each and every time?)

A few days ago, I bought a large package of yoghurt-milk cartons at the supermarket in Thailand. I didn’t compare the prices. At the checkstand, instead of scanning the barcode on the package the checker offered to open the package, scan one of the packs inside and multiply by 12, explaining it would be cheaper that way!