I think DVC members are, by definition, "big spenders." And I say that as someone who is currently in the process of buying DVC. By doing so, we are committing to years of WDW visits and thousands of dollars spent onsite with each visit. And the money we'll save over regular resort stays will make us a little more likely to splurge on some upcharge events that we haven't been willing to pay for in the past.
"Once in a lifetime" guests are also inclined to spend big, or at least to splurge on a few upcharges. Parking fees are not likely to be a deterrent to them, nor are the reduced EMH hours or the number of upcharges that WDW has added over the past few years for things that used to be free (like adding MK fireworks dessert parties in place of FP+ for fireworks).
DVC is apparently more profitable than the regular resort hotels, judging by a number of factors (including resort construction). So it makes fiscal sense for them to push returning visitors toward DVC. It just seems that the guests getting squeezed are those in between - the return visitors who aren't willing or able to buy into DVC. And that's a shame - I'd much prefer Disney to cater to as many guests as possible, and to return to the "good old days" when WDW vacations were merely expensive, not exorbitant. I don't mind that there are upcharges for those willing and able to pay for them, but those shouldn't exist at the expense of "regular" guests.