It gets even worse. They were on Sale too. So I paid like for ~4 cans.

Which makes this whole 5+1 even more ridiculous.

but i guess the 6 pack is the price of 5 cans?

That's a standard method for hiding a price increase. You start with a pack of 6 priced at $5.99. You then run a "5+1" campaign advertising this special deal at just $5.49. Great value! Finally, you end the campaign and set the new price at $5.49 × (6/5) = $6.59. Doing it this way reduces profit for the duration of the campaign, but customers won't be as angry as with a straight increase, because the actual increase in this method is the $5.49 for the 5+1, which doesn't "feel" like an increase.