Right, and even then, neither answer is going to make everyone happy. If demand exceeds supply, then prices are supposed to rise. Otherwise, if they cap attendance, people will complain that they can't find tickets. Scalping usually starts occurring at this point for most events. Although Disney can make scalping more difficult, it becomes an inefficient market where people who want to go are getting turned away.
The other answer is that Disney can expand supply by adding more party nights to keep up with demand, so that guests are more spread out (especially locals). But then people like me, who never think these parties are worth the money, won't be happy with my Magic Kingdom evenings being swallowed up with more early closures. And knowing the hungry crowds out there with money to spend, they'll just keep buying tickets until those nights are completely full too.