I have two thoughts on this and I apologize up front for the long posting but this doesn't lend itself to simple math.
My First thought is not many people are doing this. I think you greatly over estimate the use of the plan in this manner. No offense to the folk here at the DIS but on any given day I would estimate that people that frequent the DIS make up less than 1% of the visitors to WDW. I would guess that out of the DIS maybe 5%, and that would be a high number, use the Dinning plan and do the whole credit pooling thing. Then they most likely don't use it in that manner every day. So that the in the know WDW visitors about credit pooling are 1% and that 5% of them do it for half of the meals. We are talking about 0.025 percent. That is 2.5 visitors out of 10,000. So say there are 100,000 in a day and 25 people engage in this behavior. Those 25 folks saved maybe $40 on the meal whose incremental cost, i.e. food cost, was probably less than $15. That would be a total loss of $375 per day. I admit my numbers are purely speculative and have not much basis in fact except that the people in the know are really a small percentage and of those an even smaller percentage would do this. I just can't see the cost getting that high.
My second thought is along the lines of lets assume everyone is doing this and lets put it in context of the overall marketing scheme. Here I will use some real numbers from our family. Our initial plan for our trip last year was to stay off site at the Nick Hotel, rent a car, go to WDW 4-5 days and maybe spend a day at Universal or just hang out at the hotel. The Nick Hotel is more in lines with the type of space we like to stay in and I really wasn't that interested in staying on site. Under the initial plan our budget for money spent at WDW was somewhere in the $1,000 - 1,200 range. Maybe we would have 1 character meal and another sit down meal. Definitely CS meals at the parks. Then along comes the Magical Express, MYW Ticket Pricing where an extra day only cost $4 total for a family of 4 and the dinning plan. The dinning plan and the Magical Express changed our minds and we decided to stay on site at WL. So instead of WDW getting $1,200 of our money they got somewhere between $2,700 - 3,000. They litterally got every dollar we spent in Floriday except for lunch at the airport on departure day. Heck the gift shop / pin stand at WL got over $200. (I still don't know how that happend?
) And yes, we did use 4 "child" credits and got a signature meal at Artist Point, savings after paying for 2 of the kids meals somewhere around $60. Assuming that $60 is direct cost right out of Disney's pocket they essentaily traded $60 for an additional $1,500 to $1,800 in revenue. $1,400 of that was for the WL for a room that otherwise would have been empty. Somehow I think the cost accountants at Disney would love to give us $60 in food revenue to get an additional $1,800 in total spending while at the same time draining cash away from other Orlando attractions.
I think we should make no mistake. The Magical Express, which is free for for the next several years, and the Dinning plan are filling rooms at the resorts, keeping people on site and increasing the per capita spending at WDW. I know with our trip next year the only reason we will be staying on site instead of staying off site is because of the dinning plan and ME.
For those that still find it unbelievable that Disney would ever be OK with people using a credit purchased at the rate of $12 for an adult that should have paid $38, a savings of $26, could you explain why Disney provides transportation worth over $100 for free to a family of 4? The initial theory was to drive out competitors then raise the prices. Of course that theory has proven to be false as ME has been extended and is still free.