When you talk about "sales" you can only compare handset manufacturers because total sales going to one _android_ manufacturer isn't happening, therefore it becomes apples (heh) to oranges.
Apple has only recently been overtaken in handset production (not sales) https://www.theguardian.com/technology/2018/aug/01/huawei-be...
Apple's sales are slowing down faster than others. Speaking only for myself the "bravery" in removing the headphone jack (which everyone seems to have copied) and lack of a small option are what prevents me upgrading. I imagine others have similar qualms and it's really not worth upgrading for many.
That Android has dominated the $50-150 smartphone market is pretty meaningless. Those customers don't have much business value.