Just to provide a little more insight on why some people are "willing to pay": for our trip, a 5 day ticket would have cost $92 more than the 4 park magic ticket we ended up purchasing. To add a 5th day, we would have had to take a late flight home, deal with hustling to pack up and get our bags to bell services in the morning, then go to a park for a partial Saturday (6-7 hrs at best), with the need to get back to the resort by 3 hours pre-Magical Express hanging over our heads.
Or, we could add the AH ticket for about $50 more and go to MK on our arrival day, checking into the event around 6:30pm and using Fastpasses until 10, then staying until 1am, hopefully with far lesser crowds and getting some "free" snacks to boot.
So, I agree WDW is profiting off of a demand they themselves created, and that is frustrating. But it's really a pretty reasonable choice for guests to make, and a better value than many things Disney-related. Ideally, they would offer a regular late night and 1-2 late night EMH's each week during busy periods, in addition to the party nights, to spread the crowds out better. Only offering the late hours at an additional cost is just not a good look and creates some justified frustration.