So Apple has been in the news in recent weeks (at the time of writing, Jan 2018). They admitted they were
restricting the performance of older devices such as iPhone 6 and iPhone 6s to prevent random app crashes and shutdowns. Their reasoning being, as battery life deteriorates, as it does with every cell phone, the cpu must work harder and this can cause the aforementioned issues.
Apple released a statement in the subsequent days offering a cut price battery replacement for customers of iPhone 6, iPhone 6s, iPhone 7 and their Plus variants. Apple or their recognized repair partners will now replace the battery in your iPhone for just €29 (or local currency equivalent).
Full statement here.
It was an excellent response to a possible PR disaster. Apple have a knack of keeping public opinion sweet with their slick marketing dept.