https://www.theverge.com/2019/1/2/18165866/apple-iphone-sales-cheap-battery-replacement

Apple just revealed it’s expecting a $9 billion loss in revenue due to weak iPhone demand that’s partly caused by more people replacing their batteries, according to a letter issued by CEO Tim Cook addressed to investors.

Last year, Apple admitted it was throttling older iPhone models to compensate for degrading batteries that caused the phones to sometimes shut down. It ended the practice shortly afterward and offered to cut its $79 battery replacement fee down to $29 as a way of apologizing.