Since everybody needs food to survive, why doesn’t it cost more than an iPhone?
Competition. The market for food is not only broad with a large variety of substitute products (meaning if one product like apples start to cost too much consumers can just buy a cheaper alternative very easily) whereas the phone market has very few substitutes. If the (roughly) two companies who produce phones decide to charge an arm and a leg for their product, what else can you purchase? Only smart phones can do what a smart phone does. On the other hand, a steak and a dozen eggs both serve that same basic need, so if one costs too much, just buy another type of food. If you want to start selling steak or eggs its not very difficult, you don't need expensive factories or skilled engineers and programmers. Plus, brand loyalty makes it extra difficult to compete with Apple's iPhones. How many people do you know of who are pretentious about their brand of egg? Not nearly as many people who have pledged their soul to the iPhone. The market for food functions like perfect competition while smart phone producers exist in more of an oligopoly. There is a lot more to economics than supply and demand!
Under capitalism we use supply-demand as the principle for cost. Demand is high but constant because people always need food and usually the same amount. But supply is very high, the global market has in most cases exceeded the demand of what is needed.
The demand is very inelastic. Some foods are even inferior. And the Engel's effects are on their way when income increases.
Because it grows on trees.
By your logic, we should be paying through the nose for air.
You're Republican are you? What about the poor people who cant afford the high prices? They'll die then