If the market will bear the price, then it's the correct decision. In addition to the direct monetary benefits, there is probably another incentive for Disney to try getting as many people as possible to sign up for the multi-day packages and off the one-day tickets which, I am going to guess, are more often purchased on the day it's to be used: better management of their staffing, inventory, and resource needs. If most of their visitors are coming in on multi-day passes, which are generally purchased in advance (I'm pretty sure), then they have a much better idea of the levels of staffing and supplies they'll need for each day during the upcoming season, which allows them to more efficiently plan the purchase of, and logistics for, those supplies at one go before the season starts. Being able to closely predict what they'll need six months in advance for the entire season would allow them to take advantage of the efficiencies of scale by purchasing in bulk for delivery as needed, which is generally cheaper on a per-unit basis than buying day-to-day (or week to week) as needs change.