Apple dont compete on units sold, they're all about the margin. Samsung sell a lot of low value phones, which in the current environment will do well, but you'd need to sell 10 of those to match the profit on one iPhone.

This sounds plausible, but don't Samsung also sell tens of millions of units of their flagship galaxy range phones, in addition to their budget offering?

Perhaps the margin isn't quite as large as for Apple phones but the flagships are still not cheap by any means.