I think we're done here. It would be one thing if you simply stated that the enjoyment and pride you derive from your direct purchase were enough to justify the cost. That dollars and cents can't measure the security you feel when you know that you have direct points for the next 42 years. That's hard to argue with, because there's no real way to put a dollar amount on satisfaction and joy. But when you start making "mathematical arguments" using some of the most biased assumptions I have ever seen, it is hard to take your position seriously.
I wish you the best with your
DVC purchase. I would recommend that you track your usage and expenses as well as the real alternative costs for your stays over time so that in the future you can reflect upon your usage and see if it reconciles with the assumptions you are making today.