I think it's helpfull to crystalize what costs and variables are involved. Once you do that, you can just do the math and see if it makes sense.
1. your cost of funds. For some, it's the INTEREST(not payment) on the loan to get the membership. For others, like me, it would be the cost of lost income from the cash you use to pay for it. For the forseeable future, I can't make more than about 3% after taxes on the money, so my cost of money is low. But paying 10% on a loan or 18% on a credit card raises this cost way up.
2. Dues. Easy to calculate. The more points, the more dues you pay.
3. What your needs/wants in a room are.
4. How flexible you are on planning and even if you want to go back to WDW every year or two at all.
For MY needs ( a studio for a couple in the off season) the costs work out to much less than paying cash, about $1000 for 150 points, each year. That's only about 3 nights if paying cash, ($321/night with tax) but I could stretch it to 18 nights at OKW if I made multiple trips on Sun-Thurs only. That's just $55 a night! Bigger places, holiday or weekend trips, will affect the numbers.
Just do your own math based on your own situation. With 150 points, I can stay for FREE if I take one 5 night trip a year in early December, assuming principal value of points stays constant, which I realize it may not.
Cost of money (opportunity cost of $11250 @ 3% = $337) and dues (about $562) equals $900/year.
5 nights @ 8 points/night for OKW studio in early Dec. = 40 points.
Sell/rent 110 points @ $10/ea = $1100 income.
Profit $200/yr
It could vary, but you get the idea. In other cases (staying in 2 bedrooms over Christmas) it could cost way way more. But if you can stay during low point cost periods, it's cheap. Sales commissions on resale and other factors may apply.