I really don't think it's proper to use the *current* DVC AP discount in any sort of savings calculation. The current "discount" has been this large for like less than 3 months, and I guarantee it won't stay that large for long. Basing a decision on something like that doesn't make sense.
Agree with this in principle. When I was doing math on strategy about whether to do 75 direct I started with the current discount delta, and then lopped off a sizeable percentage of that to help hedge against future uncertainty. At the end of the day, you are counting on an educated (or maybe not that educated) prediction about what will happen next. That's true about ALL of these purchasing decisions.