OK, let me take another shot at it.
I did buy (1st buy, and yes, I'm already sweating buying more points) the minimum at BCV. That's enough to get us a 2BR at Beach Club in the low season (we'll often go in January) from Sunday to Thursday. The 'rack' rate for this room in the same season is $535 per night, and with taxes it's $596 (11.5% total for hotels in Florida). So, at rack rate it would book for $2883 for those 5 days. You can pretty much assume that the market price for the room 'reflects' how nice it is. These rooms (in this case a 2BR home) are comparable to premium hotel rooms. While you don't get housekeeping every day, the amenities more than make up for it, and again, trust me, they're damn nice (I was pleasantly shocked).
Now, lets assume that you can pretty much always get a 20% discount if you look hard enough. That would bring a more real cost for the 5 days to about $2386.
Assuming you buy this with Magical Beginings (you forfeit your first years points, but still pay pro-rated dues) for $74/point for 150 points. This would cost
$11100, with no closing costs (direct from Disney, not resale). If you get 39 years at 150 / year, you have total of 5850 points. $11100/5850 = $1.90/point purchase cost (yes everyone, I am neglecting time value of money, but I'm trying to make this easy).
Now, maintenance fees are approx. $4.00/(point-year) for a yearly maintenance fee of approx. $4x150 = $600 /year. Add to that $1.90x150=$285, and the 5 days cost you roughly $885.
Compare $885 to $2386 and you've got a $1500/year savings.
Now, you could invest the money, and figure out the anticipated return, say 10% historically, but you'll still be hard pressed to beat the savings. Keep in mind that dues are based on actual running costs for the resorts, which Disney can't raise for profit. I think they'll continue increase far slower than inflation and room rates in general, especially at Disney.
Enjoy!!!