I'm not sure this is true. I remember looking into this a few years ago, and concluding that the margins on the lodging side of the business were probably higher than they were in the parks---and that includes in-park spending. This article gives a nice summary:
http://www.ehow.com/info_10009736_profit-margins-tourismrelated-businesses.html
Disney's annual stock report gives alot of the financials. The "profit" is in the merch...though that can be manipulated to a certain extent. But break it down and think about it....
I can only tell you from working within the business unit that resorts are not considered profit generators...
even though they are priced at double what they should...as others have already pointed out.
The purpose of disney resorts is to fill the parks with paying customers that generate the profit in their retail outlets...
While they don't necessarily "lose" on the resorts...the money generated that can be deemed profit comes from the food court area and giftshops...just like at the parks.
Disney resorts traditionally carry a 2-1 room to employee ratio...which means that most of the lower end ones carry in excess of 1000 employees. I can tell you at a 2112 room location (mid range) 10 years back they carried a staff of approximately 1100...very high by any hotel or service industry standards. When you are near 100% occupancy all year, you have to keep a large staff at all times to turn the place over and dish out the services to an average nightly audience of 4,000 humans (not including gators).
now even if they make only $8.00 an hour...the cost of taxes and benefits and the managerial staff on top of them means that all the revenue from half the rooms are automatically gone each day off the top.
but there is a staff cost to run the service areas, buses, maintenance, recreation, supplies, logistics and support that is shared in each location, stock and food, utilities, guest services, pest control (which also sometimes falls under guest services), horticulture, magical express, IT, etc, etc, etc...
Not a very hard accounting ledger to make the resort operate at ZERO...with the same sources of actual profit being manifested in Food, Liquor, and Mickey Plushes...as always.
Even at a huge overcharge.