I'm in Auckland, and there's no Apple Store in New Zealand. The $600 price is in NZD, too, which means $418 USD.
It's not possible to replace only the battery - an AASP will replace the whole top case. I also think it's more expensive for older models, because the parts are not easy to find for a 2014 computer.
> It's not possible to replace only the battery - an AASP will replace the whole top case.
Yeah, this is true for Apple's battery service as well. I got a new keyboard and trackpad for the $288 SGD I paid.
> I also think it's more expensive for older models, because the parts are not easy to find for a 2014 computer.
This would only make sense if parts weren't ordered from Apple directly. I would imagine that they are able to as an AASP. Apple products only enter their vintage list after 5 years, and their obsolete list after 7 years: https://support.apple.com/en-us/HT201624
In this case, it looks like the AASP would still be able to order parts for your 2014 MacBook without extra cost.
The AASP got the part from Apple, but charged me 600 NZD and the parts look shanzhai (blurry printing on the cells, wrong PCB date code).
Apple Support confirmed the order number is a genuine Apple part. Makes me worry about Apple's own supply chain quality.
The AASP also did a pretty shoddy job at repairing: the case screws were in the wrong positions, and the logic board was seated badly so I couldn't plug in USB. I just spent an hour this morning reseating the logic board myself.
It's not possible to replace only the battery - an AASP will replace the whole top case. I also think it's more expensive for older models, because the parts are not easy to find for a 2014 computer.