So a year ago Len Testa figured out what Disney thinks each part of the DDP is worth. Basically with some math you can figure out what numbers solve each of the dining plans.
http://blog.touringplans.com/category/recent-news/page/24/
Counter-service meal = $10.08
Table-service meal = $25.44
Snack = $2.53
Refillable mug = $4.48
Appetizers = $2.98
30 minutes of arcade time = $0.30
Spending these amounts gets you to BREAKEVEN, you have to spend more on average to have a savings. Remember the price of the mug is a fixed one time cost and these numbers are per meal-day, which means if you are on the DDP for 7 days and get a refillable mug (retail $13.84 w/ tax) you've just paid $31.36 for it, but if you get the same plan for 3 days you only pay $13.44.
When people, like me, say 2TS is never worth it what we are saying, if you don't spend AT LEAST $50.88 (at 2009 prices) Disney has made money, ie CRT is $48.54 according to All Ears so by spending 2 credits you've overpaid for your meal by $2.34 per adult person (tip cancels out since you are paying it out of pocket regardless.)
If you leave with 2 unused Snack credits you've just given Disney $5.06. etc...
If you eat meals or snacks you wouldn't "Normally" have again Disney is making a profit on those items they wouldn't have sold you. This is all why I think before you figure out how much you are saving on DDP you need a baseline of how much you spend. Which is why I think you need to have been to Disney a few times so you know what you eat normally.
To tie into the other thread about car rental to make a shopping run. ~$30 for a day's rental plus food, call it another $70 per 3 days. $100 is 4 TS Which 2 adults with 2 meals in room plus the snacks we take into the park. So that means the 3rd meal is pure savings over the DDP.
If anyone is wondering what I get at Publix and Target: frozen breaded chicken strips, snack sized chips and trailmix, 2lt bottles of soda, 20 oz bottles of soda and water, frozen pizza, ice cream, bag-o-greens, granola bars, OJ, Milk, some type of bread and deli meat, coffee, and some condiments (mustard, dressing, splenda.) I try to pick up the sale items, but I also buy the more expensive individually packaged items for the stuff we are taking into the parks.