That helps understand the "situation", kind of like trading a dog for two cats.
You can probably buy his luger for $1500-1800 if you are patient and work at it, not his actually but another like it.
I saw several that would suffice for your wants in that price range this weekend.
I do believe he has it way overpriced , just in case someone has an equally overpriced trade!
Your idea to step back and wait for his next move is a good plan, IMO.
I'll have to look at your Navy again, but IIRC, it is a better item than a 4" common Mauser, would be to me.