I have seen a couple of non-Leicas with Elmar, so Leitz did sell their lenses to other companies at that time. I wish I could remember who made the cameras.
One Weltini was sold for $904: http://www.christies.com/LotFinder/l...jectID=3628855
It it's worth $500? I don't know, is it for you?
What you pay for is the "Leitz" name, and I don't think it's better than the one with Xenar you already have. But rare cameras are fun to own and use.
I have a Rolleicord Ia, a special version with 3.5 Triotar, made for the german police around 1939. It's in terrible condition, but I bought it only because it's rare.