Yes that was out loud, but a good point. Traditional "offset lithography", ie; big professional quality printing presses, is not really for "one-off" or short run as you say. It requires careful color separation and registration of the separate images for multiple pass printing. It is by far the best quality, and also the most expensive process. If you only want a small quantity of large prints, there are lots of places that specialize in printing with large format inkjet printers and photo process printing on transparency for back lit posters (Duratran). These are also expensive processes and you might spend several hundred dollars to get one good poster. That's why I mentioned buildaposter.com because they are very reasonably priced and you can get an estimate right on the web site.