I've got a half built 4x5 camera that I designed from scratch to be as easy, simple and cheap as possible (focusing, but no adjustments). So far it cost $10 for the lens, $5 for the darkslide, and $5 for MDF.
Like others have recognised, my woodworking skills are limited, and I'm just doing this for the fun of building a camera. It's only taken a couple of afternoons so far, and I now just need to mount the lens (currently requiring an on the fly redesign), and fix the light leaks. Should be finished next week.
Want to build a camera? I'm having a blast, and when it takes a picture I'll be proud of it. Definatly recommended.
Want a half decent large format on the cheap? Go the ebay route.