"Looks to me that this could be a good question for Paul J."
Well, there nothing like a free lunch is there? Because I was a bit lucky when I bought mine, it cost me the VAT fee price, and I have just swapped it in, plus a bit of cash, of course, for the same price. I will only know if the change over price works when I sell the Plus 4 though.
You are quite right of course, the cost of a car is what you lose between buying and selling, not the cost of the car new. Man maths is great, isn't it?