well the location of the shop, internet, and people who subscribe to comics directly from the comic book companies have their hand in that as well.
For example if people need a car to get to the shop, you have just cut off a majority of your possible customers who do not have cars! Unless public transportation is availible near the store.
It could also be the fact that most people go into the comic store and read the entire comic while they are there so buying the comic really isnt an option anymore!
It seems the only way for them to increase their buisness is to start selling things besides the usual comics, like ( hold those rotten tomatoes people!) yugi ho , dragonball z, or ( I can't believe I am about to say this!) pokemon merchandise.
Well just a few thoughts