https://techcrunch.com/2018/05/23/apple-offers-a-50-credit-for-some-out-of-warranty-iphone-battery-purchases/

If you bought a battery replacement for an out-of-warranty iPhone last year, you may be eligible for a $50 credit from Apple. The company issued a new support page post this week, announcing the rebate policy, which applies to purchases made at authorized locations.

The move is part of on-going restitution in the wake of an admission that the company was throttling processing speeds on older model phones, in order to save on battery life. Late last year, Apple apologized for not informing users about the issue, promising to be more transparent in the future.