CafeShops' paid shops are pretty much useless unless you've got a lot of sales going constantly. I just used their free shops, myself.
As for the posters at Zazzle, the price isn't that unrealistic for a large scale poster. I work at a print & copy shop in town here, and we charge about $7 (Canadian) per square foot of the poster, so the price of a large poster gets real steep real fast. The paper and ink for doing up a large custom poster is not cheap. If you mass produce posters, it's much cheaper, but for a place that does them as just a few at a time at most, the price goes up really, really fast.
Benjamin