<<You have provided your customers with X + $2,000 worth of food and services (so they haven't "lost" anything) and out of the total X + $2,000, you have paid your employees and suppliers (so they haven't "lost" anything, either) and you have $2,000 to spend that you did not have before.
<<Who "lost" the $2,000 if it's a zero-sum game?>>
The customer lost almost all of it. It's up to the restaurateur whether he keeps all of it or whether he too pisses it away in somebody else's restaurant or hotel.
The customer didn't get $2,000 worth of anything. If you add up the restaurant's cost of food, amortized cutlery, furniture, flatware etc. costs, pro-rated dishwashing, rent, water and electricity costs, pro-rated labour costs etc. you'll find that the customer paid $2000 for what the restaurateur paid $100 - - basically, he got $100 worth of food and services. The customer leaves the restaurant carrying with him (unless he visits the washrooms first) the end products and results of the goods and services he received - - a few ounces of digesting protein and fibre, a cupful of coffee etc., some few molecules of which, together with a pleasant memory, will stay with him for more than 24 hours, some harming his body, some nourishing it.
What does the restaurateur have from the same transaction? $2,000 minus the costs of doing business. Whatever his net profit is, that's what he got. More than the customer got, that's for God-damn sure. The restaurateur, if he can afford the extravagance, can spend his earnings the same way as his customer did, or he can invest them, in which case he could keep them, spinning off interest or dividends, all the days of his life. It should be pretty clear from this little disquisition as to who got the major benefit and who the minor from this little transaction.