It seems you view this as an all or none, either off property or DVC. And in large part my point is that there are both a number of options and a number of ways to get there. I've owned DVC since 1994 and we have many stays a year on average with as many as ten 1 & 2 BR villas between BWV & BCV at one time. I'd estimate that at least 80% of our stays and 90% of the room nights have been by exchange. Specific to buying DVC, unless DVC saves money over either a private rental or what you would do if you didn't own there OR it doesn't add a true additional value that has some monetary component; it makes no sense to buy. To pay more just to own at DVC than you could do so by private rental would be foolish. Certainly it's going to be more expensive in many cases than off property though not always so. And there is a spread between off property and DVC where it'd would be unreasonable to participate but that's more of a personal preference.
I am a happy DVC member/owner with both resale and direct points. My point is that DVC is foolish to buy, period. The only reason to buy is for non-monetary reasons. The breakeven point is far off compared to many alternatives. Those of us fools (me included) who do buy at DVC try to enjoy it to the fullest - and recognize we will be lucky if we get most of our upfront purchases costs back when we sell. It is a premium product compared to other wonderful vacations we can spend our money on. Given your financial values, I do not understand why you visit Disney when it’s a foolish place to own and go. It is one of the most expensive money-sucking vacations in the world. So why did you buy DVC and why do you keep going back to the Capital of America’s consumerism? (I am exaggerating for emphasis.)
It is like why do people pay a premium to buy a Tiffany diamond necklace over a non-branded necklace? There are other reasons. Like your spouse can untie the ribbon on the blue box. LOL Most economists realize that consumer decision making is irrational from an economic point of view. And marketers capitalize on that - especially Disney!
If Tuggers really want to focus solely on the most sound financial ways for vacationing, then buy the cheapest and best week you can get on the resale market that you will use every year or, better yet, rent and don't get stuck with a timeshare at all. (Okay, I admit this is a very black and white way of looking at timeshares. The point made is for emphasis.)
P.S. What are the alternatives between staying on or off property? You either stay in WDW (by owning at DVC, or paying cash through DVC, or renting points from a reseller - and hoping you get the dates you want and you can’t cancel, or exchanging in through RCI - if you are very lucky maybe you can stay at Saratoga Springs) or you stay offsite and fight the traffic and crowds (through an exchange, or by owning an offsite TS, or renting through AirBnb or elsewhere).