I don't think the math is there for the timeshares...
One more approach to the analysis -
I see the 'rent' the hotel vs 'buy' the timeshare discussion all thru here.
But you can rent the the timeshare too, without the expense and commitment of owning.
I own in Orlando (I know it's unique, in the wrong way, but the logic applies). As an owner, we pay $1,000/mo or more in annual fees. Add to that the yearly amortization of the purchase - say $500. Compare the $1,500 to what it costs to rent the timeshare on the market. At my resort, for the ownership weeks I own, I see $800-900 on the market. Even directly thru the Marriott website, the cost can be $1,400 or lower.
I tested a few other locations, and the logic holds that it's cheaper to rent the timeshare than buy - timeshares are really nice, lots of space, but you don't have to make the ownership commitment to use them, BUT it's generally cheaper not to buy.
btw, selling my timeshare and finding the price is 1/3 what I paid, and Marriott is keeping 40% for the selling fee. It's selling for about 1/4 what Marriot prices the equivalent "points" for the week we have - that point game is another set of math that further reinforces that you really don't want to buy a timeshare - just use them