Good luck, but I'm not optimistic. Most of these makers have several month waiting lists so I don't think they're motivated to cut prices. Further, Casita
are direct sales so there's no middleman's profit to undercut. I don't know about how Big Foot sells their trailers.
I think what Darwin suggests is your best bet. Maybe you'd catch someone's trailer who had to back out for some reason. I felt I received a little break when I bought a cancellation.
Taking delivery at the factory saves transportation costs.
I, too, would be interested in what you learn.