There is a difference between being cheap, and just wasting money. To have fully developed and buildable plans for a ride takes a lot of time and money, so it's a lot to ask to develop these plans for every movie considering most will never be built. Having some blue sky concepts would be feasible, but not fully developed plans. Even if they did have complete plans, it would take a couple years to build the attraction (even if you fast tracked it, it would still be at least a year), and by that point you would have lost a lot of the synergy. Personally I am ok with things like a M&G, and the Frozen Sing Along that give you a quick tie in to the movie, then letting the major attractions come later.
With that said, Star Wars is a different story since it's an established franchise with a proven track record.