I have used this particular real scenario with other posts, simply because I can relate to it: its mine. Here goes.
We have 220 pts. which costs us with dues this year $254 a month. 254 x 12 mos. = $3048. Our home resort is VWL.
Our next trip is Dec2-9 03. It will be 280 pts( we are using 140 current pts plus 140 banked pts, although that is irrevalent). We will be staying in a 2 bedroom.
According to Birnbaums, a 2 bedroom at VWL would cost $535 per night that exact same time. 535 x 7 nights = $3745.
That is a difference of $697 back in my pocket, the way I see it.
Bear in mind that even with fluctuating costs in dues( some years lower, some years higher) you will still be able to use the same amount of pts, they cant change those.
Some will argue this way of figuring is not accurate BUT it works for me. Money doesnt know the difference IMO.
I hope this helps in some small way. Know this: Disney will continue to raise its prices each year, but
DVC will Remain The Same. As for purchasing direct or from timeshare, if you can get a good deal from aftermarket and dont need financing, go for it. You still have maint. fees each year. At any rate Good Luck and hope to be welcoming you home soon!!