There was a time that DxDDP was a bargain. You could eat at a signature for one meal and pay the entire cost of the plan. However, that was many years ago. Since then, DxDDP has grown in price to the point where you need to use almost every entitlement to break even. Don't get me wrong. There there some people who can do that, but my wife and I cannot. In addition to the cost of DxDDP itself, you'll also want to factor in "extras". For example, if you want surf and turf, you'll find there is an upcharge for that. If you want alcoholic beverages, there's a charge for that. And, even if you stay away from "extras", you still need to pay a tip on what you did order.
A few years ago, we took the receipts from our previous trip and matched them to the current menu prices. We found that the cost of DxDDP at that time equaled the price we paid for meals. When we factored in the snacks, we found the "20% savings" Disney advertised at the time. Since we were taking home all of the snacks, we decided the next trip to pay out of pocket (OOP) and skip filling our luggage with snacks that were included but we really didn't want. We went to the same restaurants, ate what we wanted, drank what we wanted, and didn't bother to look at prices. At the end of the trip, we found we had saved several hundred dollars over what the DxDDP would have cost. When we analyzed the reasons why, we figured out that we didn't always want the restaurant's dessert (No HBD snack size desserts, we had funnel cake in the park later!), or that we might not have been interested in each having an appetizer (so we bought one instead of two), or we got a discount as a Disney Visa holder, and we weren't paying the tip on the "I have to take everything on the plan" amount, only the cost of the food we actually wanted. Four trips later, and we're still saving money. Our last trip, 8 days, yielded a 15% savings over the cost of DxDDP.