I love stuff like this, but I think he left out a fairly important number: the amount of time he spent making it, and the $ value he'd put on that time.
When making a single phone, this effort counts (assume $20K). Once he is ready for mass production, then this effort is negligible (divide the $20K among 100K phones) .
Ye-es... but I'd argue that's not the proposition of the video. The claim is "I made an iPhone for $300", but the reality id more like "I made an iPhone for $300 of useful spend, $700 of wasted spend and $20,000 worth of my time".
The watcher might be tempted to take away "I can make an iPhone for $300," but actually it's more like "I can make an iPhone for $300 and ~$5,000 of my time".
Obviously the "$5,000 worth of my time" is actually the fun part fro some viewers. If you're the right kind of maker it might even be worth $5,000 to you.
I assume that most people asking this question of how much it costs to make an iPhone are asking in the context of a hobby project. In the context of a hobby project, at least for me, the time spent doing something I enjoy is a benefit, not a cost.