Why, do you know where it is?
The Smithsonian traded a complete Nieuport 10 owned by Nungesser to Cole Palen for an original Nieuport 28 built from parts of unexceptional lineage. Neither was a combat veteran airframe, but Nungesser was known to have owned and flown the N.10 and had his black heart logo painted on it's side. Who got the better deal?
Value is determined by the desire of someone to own the item being sold. With unquestionable documentation, in the condition you describe, the Udet combat veteran Fokker D.VII "Lo" would still sell for less than $5,000,000 IMHO. It would be of interest mainly to WW I historians.
An original MvR Dr.I would be much more valuable than any other WW I airframe as an investment, because everybody knows "The Red Baron". Ask 100 people on the street who Udet was and 99.5 of them won't know.
I bet the Smithsonian would trade you their restored D.VII and a couple of other airframes from the collection for it though. I'd be willing to trade it even for their D.VII, D.Va, and SPAD XIII! 8)