I went solo to WDW this past May and was on the DDP, but I did get the totals at each meal just to figure out what I would have spent without the DDP. I did order an appetizer, entree, and dessert at each TS, but did not necessarily order the most expensive thing on the menu (just whatever I was in the mood for at the time). I just looked at my totals and for CS I spent $10.07-$28.37 (Earl of Sandwich and Pepper Market at CSR), for TS I spent $32.36-$62.58 (Cape May Buffet and Le Cellier). My snacks ranged from $2.95-3.99 (Doh Bar and hot caramel sundae). Anyway, as you can see they had a wide range in prices. It's going to depend on where you eat.
FYI: For eight nights I spent $311.92 for the DDP and ate $31.79 in snacks, $121.25 in CS, and $405.11 in TS (total=$558.15). So I guess you could say I saved $246.23 with the DDP, but then again I probably would not have ordered all those appetizers and desserts, if I hadn't been on the DDP. My TS meals were Le Cellier, Cape May, Konas, Spoodles, Wolfgang Pucks, Turf Club, Chefs de France (lunch), and Rose & Crown. For CS I ate at La Kringla Bakeri, Wolfgang Express (twice), Pepper Market, Starring Rolls Cafe, Tusker House, and Earl of Sandwich.
I'm using the DDP again for my Sept/Oct trip, because I got it free via the Bounce Back Program, but when I go back in Dec I won't be doing the DDP again, because it is just too much food and beside I can save almost as much with my DDE card.