Funny, I think the prices are high for the same reason: It should cost much less than retail to make something.
Not that I'm faulting them at all. They're almost certainly geared for people who want to hand out examples of their most polished work, and maybe create the occasional keepsake. In that case, they are the retail market, so the price tracks.
Thinking of it from the perspective of, say, "I'd like a full run of some Centaur titles," the price becomes prohibitive quickly. And if you were (again, picking a random example, though if someone does this, I'm your first customer!) build a new incarnation of Centaur by reprinting the old books and transitioning to the new, either the final cost is enormous or the profit margin is nil.
At that point, you're probably better of scrubbing the comic form-factor and looking into book printers, instead.
