I helped set up the inventory database for a small amusement park, part of it was food cost analysis. We even called up Pepsi to ask them what the typical CO2 use was so we could incorporate that. IIRC a 32oz soda cost 7.2 cents and was sold for $1.75. Like .04 was the cup which was a custom printed cup for the park instead of the cheaper pepsi branded stuff.
Whats kinda messed up for many places is that Pepsi/Coke sell alot of their prepackaged products (cans, 2 liters, etc) to restaurants for more than you can buy them for in the store. We were paying I think 8.60 per case for cans when you could regularly purchase them at stores for $5.00. Of course they are “not labeled for individual sale”
I worked for a pizza place that claimed a single topping pizza averaged $1.80 in food cost, we sold it for $12.99.
Where I work now we sell posters. One of our internal divisions prints them. We pay something like $.17 each for them and sell them for $3.99. near the end of the year we put them on sale 2 for 1, arent we generous 
If it dosent sell after a year or so we mark them at a dollar and they rarely come back.
There are many costs associated with some of these businesses that we really don’t factor in here(insurance, health and hazmat permit issues, not to mention labor, facility, taxes).
$.03 per gallon on 10,000 gallons of gas is only $300 a day profit, you cant pay one person 24 hours a day, and a lease on a 1/2 acre lot on a busy street for that. There has to be a little more in it then that. This is based on a non mini-mart type place.
I was under the impression however that as a general rule a restaraunt runs about 20% food cost. So your $15.99 steak dinner with fixins cost them about $3.25 for the meat, potato, veggies, etc.
Alot of alcohol although quite profitable dosen’t make quite what you think. The taxes on alcohol for resale are astronomical. I don’t have specifics but I know they’re ugly. The thing that allows alcohol to make a decent profit is since it is expensive to start with a lower percentage markup still pays the bills. Any bar owners/managers out there with specifics? I know they are not allowed to just stop by the liquor store and pick stuff up, big no-no. You have to buy it through distributors who add the appropriate taxes.