The original 'fake' bill was $340, the target is $450, that's a delta of $110
4 drinks = $110. Even at WDW prices that is pushing credulity. In fact I took a look and the most expensive alcoholic beverage that is on the menu that is allowed by the plan (remember, sparking wines are plan approved, champagne is not - an other example of being dictated by the plan) is $17. Lets say everyone orders the most expensive drink on the menu. That is still only $78. Approaching $110, but not quite there.
Lets look at this an other way
The Standard DDP is $74 and change per person per night. For sake of argument call it $75. Call the TS portion $50, and the Snack and QSFB offering $25
In the case of CRT, OOP is, with the most expensive drink included, $340 for the meal + $78 in drinks = $418 With it "costing" 2 credits each on the plan, it comes to a $400 value. in this case you save $18. However everybody had to get the most expensive drink to make the numbers work. As soon as people start ordering soda, the benefits dissolve.
Most places on the DDP are like this. If you get the most expensive stuff on the menu, then the plan is cheaper. But, as soon as you get cheaper stuff, it looses value. If you are getting expensive things just to make the plan work out when normally you would not, then you are not saving money.
Remember, Disney has been running their business for years, they know what they are doing. They would not offer the plan year over year unless there was some financial benefit to them - i.e people somehow spending more money than they would have.