Someone with more energy or economic knowledge can work out the relative cost if they're interested, but 30 years or so ago comics were 35 cents and sold in every supermarket, convenience and liquor store. Yeah, in addition to being a taste thing it's a question of access, both in terms of availability and cost. Comic shops were not the only venue to grab the monthly single issues in.
Now those singles can really only be found in comic shops, and they run US$3~4 per issue.
With the sale of trade paperbacks in Barnes and Noble and Borders, comics get a new market, a new audience, but I bet there is a dangerous marketing gap between the sales of any given monthly single and whether or not the publisher will commit to at trade paperback edition. So there could be some comics which might have flourished with access to the audiences of an upscale bookseller, but instead tanked from bad single-issue sales before it got that chance.
BTW, didn't Sony announce that comics would be part of their PSN strategy for PS3 and PSP?