Walt,
The thing most people forget is that WDW has more than just theme parks and resort hotels. There are production facilities for both TV and movie projects. There are corporate training centers for front line and management personnel. There are construction facilities for the manufacturing of attraction and entertainment sets and backdrops. There are product design offices where various ideas are generated for Disney merchandise.
Sure, many of these functions could move most anywhere – but not without some cost. My guess is that Disney probably envisions relocation of some of these functions, such as the movie studios, when they need the space at Disney World for new theme parks and resort facilities, but that is clearly several decades, or even a century or two, from now. In the meantime, the company retains control of the land and using it for these purposes saves the cost of procuring land elsewhere.
There are also little “gotchas” in the cost factor. If the product design offices are near the parks, the staff can take prototypes into a park to gauge reaction of park guests fairly easily. If they are not collocated, that’s a much more expensive proposition requiring employees to travel to the park at the company’s expense. Flights, local transportation, lodging, and per deim for meals and incidentals easily add up to a couple thousand dollars per trip.
Norm.