According to Mixpanel, the iPhone 6 makes up 5.86% of the iOS powered handsets that it tracks, vs. 1.28% for the iPhone 6 Plus. After the opening weekend, when 10 million units were sold according to Apple, Mixpanel had the iPhone 6 accounting for 3.22% of active iPhones with the iPhone 6 Plus responsible for .47%. Taking the change in the numbers since the opening weekend into account, and averaging the increase in both new models, it shows that Apple has sold more than 21 million units. The Apple iPhone 6 would account for 17 million in sales vs. 4 million for the larger phablet.
Apple is working feverishly to get production of the Apple iPhone 6 Plus up to speed. Until that happens, Apple could be faced with lower margins than expected as some would-be iPhone 6 Plus buyers give up the hunt and opt for the lower price iPhone 6 instead.
source: Mixpanel via Forbes