perhaps a bigger issue would be environmental impact. On the plus side for monorails, the cost of the Las Vegas monorail was $87M/mile but experts believe it can be built for $50M/mi. Linking resorts would increase their value and therefore the cost per night. It would reduce the number of busses and risk exposure of accidents as well as be environmentally friendly. And Disney knows they can dramatically increase the traffic at Downtown Disney (I've seen estimates in the past of double the current traffic) by linking it to the monorail. If the monorail led to $100k/day in extra spending just for linking in Downtown Disney, that's $3M/mo or $36M/yr or a payback period of just under 10 years for 7mi of track.
There would be additional cost in having to realistically relocate the TTC to somewhere closer to Epcot. Let's assume three loops: MK, Epcot/MGM, Downtown Disney/AK with resort access (single loops, no express). They could extend the Resort loop to the existing Epcot track, add the Wilderness Lodge, and loop it just north of Epcot. Loop the Epcot track at the same point and extend it south along the waterway to MGM. Create 3rd loop looping to Downtown Disney, behind Typhoon Lagoon to AK, to AKL, eastward just north of Blizzard Beach and then north along the entrance road from 192 to the new TTC. A fourth loop would be the long infamous light rail to the airport.
Creating this kind of a setup would add Wilderness Lodge, Yacht & Beach Club, Boardwalk, Swan & Dolphin if desired, AK Lodge, and potentially other resorts to the monorail (CBR, Port Orleans, etc.). In addition new resort locations with monorail access would be established. Of course it would also bring Downtown Disney, Typhoon Lagoon, and possibly Blizzard Beach closer to the guests (who likes taking 2 buses, waiting for one for 30min, or having to figure out how to get from A to B). Having four resorts per line would be optimal.
Looking at the economics, let's assume this adds 20mi of track at a cost of $1B ($50M/mi) plus additional costs of $300M for a total price tag of $1.3B. For a 20 year payback (it would be amortized over 30yrs so the final 10yrs would be 100% profit - operating expenses) that would require an additional business benefit of $65M/year which comes to $180k/day. If you raised the cost of the 35,000 hotel rooms $4/night that would cover the cost in itself (assuming 75% occupancy) assuming NO CHANGE in room rates for resorts newly attached to the monorail.
I would appreciate comments/feedback.