With a dinner at Whispering Canyon, breakfast at Akershaus with the princesses, a lunch at Sci-Fi, a few uses at Artists Palette (one of the few CS that take the DDE), our family of four broke even on our 4 day trip. We have 2 more trips this year, for another 13 days total, so it will be totally worth it for us.
If you don't do many TS meals, it would be much more difficult to cover the cost.