There's some evidence that guests have switched spending from sit-down dining to Lightning Lane. Most of Disney is thrilled with that.
IIRC, the price of a Disney food item cannot exceed 25% of the cost of ingredients + labor to produce it. So a $60 steak costs Disney $15 to buy and cook.
That doesn't count the cost of operating the restaurant or all of the support staff that goes into running it.
This article says that's 35% on average. Disney doesn't pay rent, but they do have to set aside money for building maintenance, upgrades, taxes, etc., which is a component of rent, and it's probably considerable for Disney. Let's say that's 25% instead of 35%, and note that I could be wildly off on this one.
So a Disney sit-down restaurant's gross profits are 50%.
Lightning Lane revenue is something like 96% profit. (~$750MM in annual revenue on $25MM to run the program)
Disney would trade $1 in restaurant revenue for $1 in Lightning Lane revenue all day long, given those margins.