Nothing could be more horrific to consider than the destruction of Napoleon's army in Russia; I have deliberately avoided researching it or going into it because I wanted to limit my focus to the last two battles of the Napoleonic era in Europe where we end it all at Waterloo.
It is interesting that this particular letter, concerning a threat that never happened, went for 150,000 euros. Did someone drive up the cost? Is it really worth that much?
My guess is that there are so few remaining privately held documents like this that it was worth every penny to whomever wanted to preserve it.