Pay money to buy free stuff

I saw something that really got on my nerve today during lunch time when I was shopping at supermarket near workplace. I saw two brands of generic distill water. One selling at HK$1.99 and the other one selling at HK$2.99. OK first of all, the idea of bottling free stuff and then sell it for a price already enough to make me grin my teeth. But the fact that there's a 33% price difference between two GENERIC brand name of DISTILL WATER is just crazy. I turned both bottles of water around and read the specification. They were both freaking the same. HOW can one charge a buck more than the other EXACTLY THE SAME PRODUCT. I mean, I feel like they might be even from the SAME factory, and I don't see that freaking greenish blue pigment on the plastic label that much more expansive than the white blue one!!! This is a crazy world I am in.