Not sure why it would be important that it not come from a dealer. I don't know where else you could get one, but probably lots of parts suppliers would have a source.
I would expect a band new frame to cost a pretty penny.
The advantage of buying a used one could be all the small parts and accessories that would come with it for very little money.
I recently bought a used 1-ton frame for $4600. It came complete with a running 454, four-wheel-drive, a nice interior and lots of shinny black paint.
I've been driving it almost every day since. I do expect that someday it will be a parts donor for some project, but not until its covered a few more miles.
