So, if they are the only ones with the item you "need", what is your alternative?
Walk out and do without?
I suppose if you live somewhere where there is a choice, and/or you have figured out that access to the internet is a good thing (strange as it may seem, there are still a lot of computer illiterate people out there, and lot of them are around here), but around here, there really isnt much choice, unless of course youre willing to drive 75-100 miles to one or two other places that might come close. Assuming you even know of them.
So when the prices more than double overnight, and on stock that is already "on hand", and you arent someone who understands that you should be buying all the time, so you arent caught short, what do you do when you really "need" something, and they are your only choice?
Yup, you pay the gouge and grumble. Its that, or do without.