depends on what you consider to be the market(s). the north and south sides of the playground might have rather different valuations of a card. if you can realize that and safely transport your goods that distance, you've got an opportunity.
I guess that when I think of kids trading cards like Pokemon or Baseball cards, I envision kids from different social strata all religiously reading the Pokemon websites and having a similar idea of the value of the cards.
But having done no card trading of any kind myself, I wouldn't really know, that's just an assumption based on a few observations and anecdotal evidence.
