Assume they can earn 5% on their cash hoard with smart, conservative investments.
If they have a $600 phone (they sell them all for that price) at sea for 1 month they would have earned about $2.50.
They sell the phones as fast as they can make them, and if they don't have a phone in stock and someone desperately needs a phone, they may buy an android, so that's revenue they'll never see again.
When we're talking about $0.40 savings to have to delay $600+ in guaranteed revenue by a month. That's all I need to see to know do air every time.
Of course we also know that Apple manages their entire supply chain with just 5 days of inventory in stock at any give time. Much harder to do that with ocean freight.
one thing that probably skews me is time... air freight has probably gotten cheaper continuously over the last 15 years..
given the problems when there is a lack of supply of phones, i'm still dubious that air freight is the standard option... such shortages last longer than a week.
is there any evidence of what they actually do? i'd put my money on boats. iphones don't magically devalue in transit afaik and the lead time is short enough to be practical... it just makes no sense, from what i understand, to use planes unless its an emergency.