It depends on where one goes for food in Iceland. Soft drinks and the like tend to cost around $3, American. Fast food prices range at about the same price as they do in the United States. However, going to a sit down restaurant can range from $15 to $40 for one meal, depending on what is in the meal. Lamb and more traditional Icelandic dishes tend to be pricier, ranging from $25 to $40, American.
The reason the food and drinks are so cheap in American dollars is because the Krona - the Icelandic choice of money - is rather weak after their economic crash in 2008. The current exchange rate is about 110 Krona to $!. The Krona is about as strong as a penny - not very strong at all.