Go for it if you want! The sales data is available on the DVCNews website.
Of course, there is an easier way to estimate revenues generated for VGF: DVD has sold about 2.46 million VGF points. Take that number and multiply it by whatever price-per-point number you want to use. $155/point yields $381.3 million; $160/point yields $393.6 million.
Remember, since VGF never had any incentives offered, the advertised base price is reflective of the purchase prices for that resort. Such is not the case for AKV, BLT, SSR, or Aulani. A large percentage of the sales for these resorts involved tiered incentives.
Personally, I'm not sure what you'll accomplish be undertaking such an exercise. Once you estimate the revenue generated by sales for a resort, then what? How do you estimate costs for the planning and construction of the resort? Commissions for the sales staff? Costs of the DVD support staff? Costs for advertising and promotional material? Without some hard data to substantiate these amounts, whatever net revenue amount you end up with is just a wild guess.
We all know that Disney makes a profit from building and selling
DVC resorts. Does it really matter whether it made $100,000 or $100,000,000 in profits? In my mind, the amount of profit realized by Disney doesn't diminish my use or enjoyment of my DVC membership.