@phaZed As someone who works on Macs a lot, you're not missing much. If you enjoy wasting hours and hours of your life for little return, then get into Mac repair! I just replaced a battery on a 2015 MacBook pro. You have to literally strip the Mac down to the last screw because you can't just replace the battery (it's glued in), you have to replace the battery + keyboard + trackpad + palm rest and re-built the ENTIRE computer from scratch around this part in order to replace the battery.
We're not an Apple authorized service provider (AASP) so we can't get parts from Apple. We have to buy third party. Not that it matters. A 2015 is "too old" for Apple to even repair or stock replacement parts for.
So anyway, I spend over an hour rebuilding this laptop from scratch and when I fire it up, the battery won't charge and under the status it says "Service Battery." F(@*%*@*# my life! Now I have to call the customer and explain that I bought a bum part. Assuming they're understanding about the whole thing, I then have to deal with returning this part, buying another one, and then doing the whole procedure again next week! If the customer isn't understanding, they'll just say forget it and I'll have sunk nearly 2 hours into this client for nothing.
On the flip side I also sold a desktop today for $2,000 to a business customer of mine. My cost was about $700. Total time invested: 1 hour. Unless I'm getting paid $1,000 to replace this MacBook Battery (spoiler alert: I'm not), it's just a waste of my freaking time compared to clients like this.
It's gotten to the point now where I don't want to actually fix Macs anymore. If someone comes in with a Mac, I'll try to sell them something else (another Mac or (preferably) a PC) with data transfer. I have good relationships with several vendors who can get me Macs. I think I'm just going to do Mac sales from now on. I have no desire to spend hours stripping laptops with teeny tiny screws and dealing with adhesive and BS. Pre-retina MacBooks were great but this new stuff is just garbage.