We often share a QS meal at lunch time. Portions are always generous, and unless you are a huge eater, something like 1/4 chicken with 1/4 slab ribs with slaw, beans, and corn bread really will feed two- if not sure, get a side with it. We also find that we don't eat as much at meal time at Disney as we do at home; not as hungry in the heat/humidity, often somewhat filled from water consumption, and of course we snack at Disney, which we wouldn't do at home, so that keeps us partially filled, too. We usually bring stuff from home for easy in-room breakfasts, share a QS for lunch, then each have our own TS at dinner. One thing that kills my budget is that we like to have a glass of wine/mixed drink (or two) with dinner, and alcohol is hugely expensive at Disney; figure $10-$15 per drink. This past trip DH and I tried sharing a glass of wine with dinner (or sharing two glasses) and found that this worked pretty well in helping to cut that cost a bit.
I usually figure $15 per QS meal and $50 per TS (or lounge) meal- we don't do apps or dessert usually- and then add 25% for tax and tip. Close enough... although I do think we spend more than that with the adult beverages. Sometime I'm going to get a Target REdCard and buy discounted Disney gift cards before we leave to help with the costs (if I don't have enough VISA rewards saved up).