I was thinking of selling my old 2014 MacBook Pro 15" to maybe get a new Mac and I noticed the track pad wouldn't click very well. Upon further inspection I see the battery had swollen up and was pressing on the track pad.
Took it into Apple ready to pay $199 for a replacement battery.
Turns out it also needs a new top as part of the replacement - and the total would be around $450.
It's been out of warranty for over 13 months.
Apple said they'd do it for free. 3 days later had the Mac back and has a new battery and top.