A. What it's worth to you.
As an example a friend and I have just invested many tens of thousands in our aircraft. We know we would not be able to sell it for anything close to the cost to us. We have insured it for a figure between those 2 numbers and would not consider selling it for at least 120% of what we paid.
All that said I agree with most of the above posts with one proviso - add in how much the group size and personalities are worth to you.