What makes you think that everyone who is not a DVC member is simply an "occasional" visitor? Seems like there are an awful lot of folks on these boards alone with signatures listing dozens of stays at resorts like the Grand Floridian, Polynesian, AKL, All Stars or a dozen other resorts. I wasn't aware that we could actually determine that there are only 90,000 "loyal" Disney guests (and DVC members) as opposed to those other tightwad schmucks Disney senselessly caters to...
But here's some real data: There are about 22,000 Disney-owned guest rooms at WDW vs. about 1600-1700 DVC rooms. I think you're grossly overstating the importance of DVC members in the grand scheme of things given the fact that we represent less than 10% of those staying on Disney property at any given time.
My wife and I honeymooned at WDW in '97 and spent over $1500 during the trip AFTER our transportation, lodging and tickets. That's $1500 over 7 nights for food and souvenirs alone. As DVC members, we don't spend half of that amount during a trip now, and our trips today include two kids.
For every DVC member you would label a "die-hard" there are folks who spend minimal or ZERO time and money in the theme parks.
Do DVC members spend more, on average, than cash resort guests? I don't know if I believe that's true or not. Even if so, by how much? 5% more? 8% more? Whatever it is, it's certainly not enough to offset the reality that we are just a drop in the bucket of the entire population Disney hosts on a daily basis.