It would costs very much. Maybe 15000$ would do, but there is an upper limit of 5000$.
You could try $5000 plus 5000 limit of every thing else and - if still not enough - trade them some of your old ships. I would not be surprised if the trade will still be refused.
But if you find yourself in the Axis and at war with France - if you can grab 5 French provinces and include those in the trade - that might work after Vichy Event fires so you own those conquered provinces (to be able to trade them away). If I am right, playing as Spain, the next event "return of Provinces" regarding the normal Vichy provinces will not include any that you grabbed before Vichy fires. So, if you had Marseille (normally a Vichy province) you would be able to keep it. And Bordeaux (easier to get and not part of the "return provinces to Vichy") would be worth quite a lot to Germany. Those two provinces and another 3 French provinces plus 5000 of everything else might make for a Bismarck sale! In any event, it is the limit of what you could offer at any one time unless you also got plans Germany don't have (very doubtful).
However, I am not really positive that - if you are playing Spain - the event "Return Provinces" actually will not simply boot you out of Vichy's provinces. I do know for sure - if you play Germany and you Militarily Control Nationalist Spain, then Spain will keep those provinces.
But from Dax thru Bordeaux and on up the coastline are all non-Vichy provinces that Germany really wants. So trading to Germany Bordeaux, Cholet, Nantes, Lorient and Brest probably will succeed to trade for a Bismarck (plus dollars, supplies and resources as might be needed).
Spain attacking France I found very interesting and hope it works out OK so you can get that Bismarck.
