The size of the products when comparing the Air to the mini probably doesn't have a lot of bearing on the actual cost of the materials. The panel gets cheaper, I'd imagine (although keep in mind it is a physically smaller panel with a higher pixel density), and maybe they spend 10 cents less on aluminum, but nothing else really scales down. Same cameras, same USB-C connector, same microphones, similar speaker setup, same storage modules, same Pencil magnets, same TouchID sensor, same WiFi and Bluetooth modules, same cellular radio, same gyro/accelerometer, etc. Oh, I guess the battery is smaller too. I'm not really displeased with the price difference from the Air.