See, this was my thought, too. I suppose it IS a 20% price drop. But, it's just still an insanely expensive price. Plus, there's just something unsavory about having daily admission to a park, then being told you have to leave, but can buy another (more expensive!) admission ticket to come back in on the same day.
Please don't take this the wrong way, but if you're questioning the expense, then you are not the customer that Disney is looking for. Disney is looking for high margin guests, ones that would partake in these type events without care of cost (or quality).
Maybe this strategy will work as a way to clear out the parks, but then again maybe it will drive everyone over to USO who seems to want anyones and everyones business. (Think Apple iOS and Android product and marketing)