That depends. You have never been charged for 5 star food in economy because they don't have 5 star food in economy. They have 1-2 star food, or maybe 3 at the very most. My food is basically first class celebrity chef Emirates food delivered to economy class, without having to buy a fist class suite. I think it is reasonable to charge that amount if the food is the very best food.
I have flew Turkish and Swiss, I haven't had to pay for meals and I would say the food would be 3*-5*, even in economy, that's realistic quality for you there. now lets compare that to my Thomson flights, where food had to be payed for. It was about £7 (or about $14) for something on AE probably rated as 1/2* so paying anymore I would consider as spam, as even an LCC doesn't cost that much to eat and drink on board.