It all has to do with the rental rates Disney is charging. If the rental rates increase ( as they have) the "value" of any piece of "real estate" increases with it.
For example if the rental rates ( 10 years ago) were $200 a night for 10 nights a 50 year "program" has a simple "value" ( ignoring inflation ) of $100,000 ( 200X10X50)
If the rental rate now has increased to $300 a night the "simple value" of the same ownership with only 40 years remaining has increased to $120,000 ( 300 X 10 X40).
Lets say that 10 night stay in 2040 to rent is $50,000 per year. Compare to dues cost is $10,000 then $30,000 to buy a membership ( total cost $50,000 for 2 years vacations , still looks a good buy when compared to rentals cost $100,000)
Now I know I've used VERY simple math, but most people, financially, don't understand or try to understand factoring in inflation etc into such calculations.
One of the "measuring sticks" applied to investment ( and
DVC really shouldn't be viewed as an investment) property is : The true value of a piece of "property" is a multiplier of the rental rates of similar pieces of property. I.E a shopping plaza that rents out units at $20 a sq foot per year has a higher purchase price than one that rents out $15 a sq foot. A condo that rents at $1000 a month ( generally) will have a higher price ( probably about 25% higher) to purchase outright than an identical unit that is in an area that only commands $800 a month.
IMHO the point cost per night of different resorts is less of a factor than inventory supply and demand for those resorts. VWL and BCV have MUCH less resales than OKW + DSSR because there is MUCH less inventory at those. Coupled with home resort advantage ( with less supply at BW area) makes resales at higher costs. Less supply and more demand.