The Objet1000, the world's largest 3D printer as of December 2012, has a work envelope of 1,000mm x 800mm x 500mm at a 16 micron resolution. This image shows the scale of the Objet1000, definitely not something for the living room hobbyist.
Just read an article today elsewhere about the expanding 3D printer market. The gist of it was that a main area of expansion will be manufacturing contract shops that would invest in the printers and materials and then become the go-to place for people / companies that have the need but not the resources for the equipment. Sort of like a Kinko's / contract manufacturer combo. It seems like this would be a good product for a business like that.
The more durable plastics for 3D printers--used for auto and airplane parts, for example--generally go with the higher-end very expensive machines, since they're aimed at industrial apps, not at individuals or prototypes.