You're shifting the goal posts. You said "overall ability doesn't mean much." It obviously does, otherwise Wout wouldn't be paid what he makes. Does it mean as much as winning the top monuments? No. So MvdP makes more. It doesn't seem that I'm saying anything controversial here, just saying what should be obvious to anyone paying attention to cycling.
Looking more closely at the salaries, VdP is 4th, Wout is 5th, with half a million euros less (and more than Remco). So, it seems that overall ability, contrary to your claim, does mean "much" after all.
Gazzetta dello Sport estimates pay for the top-10 earners in the WorldTour – and there are a few surprises.
velo.outsideonline.com