Not quite a complete explanation. First, the "law" is misnamed, since it isn't like a law of physics, which explains how something works, but is instead more of a drastically simplified model, meant to exhibit not how the market really works, but to show how one factor would affect the markets, if only that factor mattered.
Under that model, a decrease in demand causes prices to fall because suppliers are presumed to want to sell everything they have produced. Alternatively, suppliers respond to a decrease in demand by dropping production so that they don't need to drop prices to sell everything produced. But that only holds in a market with completely flexible supply and demand.
With WDW, the supply is not flexible, and Disney does not need to sell everything. Rather, they will set prices so that demand is equal to or less than the available supply (max capacity) in the way that maximizes total revenue. The basic model assumes the markets are looking to sell a particular quantity, but In a business with inelastic supply, letting some go unused can maximize total revenue, if the demand curve is inelastic as well. So, if raising prices by 5% only causes a 3% drop in demand, you come out ahead by raising prices. And if dropping prices by 5% only causes a 3% increase in demand, you come out a loser despite the fact that you sell more.
