If I purchase an aircraft that I am currently leasing what is the price based on? The original purchase price of the aircraft when I leased it or the "book" value?
I'm sure someone can tell you the actual answer, but a quick look at my leased aircraft - If I get a quote to buy it (and I assume that price includes some early lease termination fee) take off the early termination fee that they quote me the net figure looks similar/slightly higher than the current used market which would suggest, given the current aircraft inflation, that it's the current market price rather than the price it was when you first leased it.
But that would then be your book value if you bought it.