Your parenthetical is very important -- and therein lies one of the reasons a lot of people think the DDP is a misleading waste of time and money.
If you ask yourself, "did we pay less than we would have if we'd bought the same items at the menu price?" the answer will be "yes" some of the time, as it was for you.
For many, however (myself included) the relevant question is not whether the DDP costs less than the same overpriced items OOP. I'd prefer to decide for myself what food options offer me a good value, and not let Disney attempt to convince me that one meal is better than another by virtue of Disney's otherworldly pricing. For me, the pertinent question concerning the DDP is, "did we pay less than we would have if we'd paid out of pocket FOR WHAT WE REALLY WANTED TO EAT, AND NOTHING MORE instead?" That is, if we booked at the restaurants at which we most preferred to eat (regardless of their menu cost or number of DDP credits), when we wanted to eat (not trying to eat only dinners, the most expensive meal at most places), and ordered the food we'd most enjoy (rather than what was priced the highest, or what "fit in" to our meal allotment), and didn't order things we didn't want (e.g., ate snacks only when we really wanted a snack, didn't overeat for the sake of "getting our money's worth," didn't order desserts and fountain drinks that we wouldn't otherwise care to have or for which we feel too full, skipped a meal or had a granola bar in our hotel room when we just didn't feel hungry). If that's the question we ask, and even considering that we still do our fair share of vacation-induced splurging and overeating, my family always comes out way ahead paying out of pocket...