I recently bought a 10 year-old iMac second hand from Cash Converters, which I promptly softbricked the day after purchase (bad Bootcamp install + firmware password).
I took it in to the Apple Store, and despite the fact that it was 10 years old and used, they contacted the engineers in Cupertino to get the firmware unlock key, reformatted it and updated it to the latest supported macOS, and didn't charge a cent for the service.
I was blown away and told people I knew about the experience. Apparently they did something similar for a friend's iPhone 6 a couple of years ago. Didn't charge a cent to service a 5 year-old smartphone.