While I cannot answer your questions directly, I can give some related information. I worked at Arby's for several years. Arby's buys roast beef for $60 which after cooking weighs right around 152 oz (9.5 lbs post cooking weight). Thus $60/152 = 39.5 cents per oz. Add in the cost of storage (freezer and refridgerator), cooking (oven and holding oven), waste (not all the beef can be used), and labor (for preparing the beef) the average cost is right around 50 cents per oz. Now look at the menu prices. Arby's charged 29 cents + 50 cents per oz of beef (This was 5-10 years ago, the prices may be different now):
2 oz junior was $1.29,
3 oz regular was $1.79,
5 oz giant was $2.79.
I don't know what it cost for the bun, butter for toasting, wrapper, labor, machine wear and tear, and electricity to make the sandwich, but it is probably quite close to that 29 cents. Arby's pretty much does that with all their sandwiches - they don't make a dime on them. In fact on their 5 for XXX deals they lost money on each sandwich. Where do they make their money? The pop and the fries. A pop costs 2-3 cents and they sell it for about $1.
Now most fast food joints have similar policies. They make no money on their sandwiches and then make the money on the fries and pop. So I'd expect the McDonald's and Burger King to be similar (I don't have hard numbers, but I'm pretty sure this is true for them. They probably only earn a few pennies per burger). Pizza on the other hand is different. Pizza joints don't sell enough pop and extras to survive from that alone. So the pizza is where the money is at.