The price of the meal in Cappadocia is totally depending on what you would like to eat. The lunch price is usually cheaper than the dinner and there are a lot of fast food restaurant serving cheap, yet delicious meal for about 5-10$ per person. If you would like to sit and eat in a restaurant, you might expect to pay a little more around 10-12$ per person.
The dinners are usually more expensive than lunches and you might expect to pay around 15-20 $ per person for the meal + the drink you would like. There are more expensive and high-end quality restaurants that you might pay up to 40 $ per person.