According to IHS iSuppli via Macrumors, the components on the new 16GB iPhone SE are estimated to cost about $160. IHS rounded up the figure from $156.20 to $160. The reason it isn’t as expensive as the previous models (iPhone 5 was estimated to cost about $199 and iPhone 6s about $236) is because Apple used a number of parts from the iPhone 5s, 6 and 6s.
Also, these parts don’t cost as much as they did. For example, the iPhone SE’s Gorilla Glass display cost about $20 as opposed to the $40 price tag when it was first used.
While it might cost so little to make these devices, you must bear in mind that you are also paying for other things like Advertising cost, R&D, and others.