The lesson I learned is do your research. I didn't think Apple would even touch an out of warranty phone to replace the battery, but apparently I could've paid them the same price as I paid the 3rd party folks.
I've always run into "It's more than 2 years old, we aren't even going to open it up." with Apple. Now I could've been dealing with incorrect info, but I just trusted that the reaction I'd always get trying to bring an older product into the Apple store would be the same stuff. But apparently not, they WILL replace the battery for $79.e
I had the 4S and 5S and neither had significant battery charge loss at 1.5 years. This was extremely significant with this phone. I've never had a real issue with an Apple product before that I couldn't fix with my own troubleshooting (minus the iMac issue but it WAS old-old) I assumed I was running too many background apps or something. I've monitored this since June (and auto app updates are off too) and it's only gotten worse. I figured Apple MIGHT honor a refund difference since this is a known defect now.
A few years ago, Apple would NOT open up a 2 year old iPhone UNLESS there was a manufacturer defect.
I know I'd have absolutely no case if something went wrong with the phone at the hands of a 3rd party repair place. I didn't think that hard about asking this question, because nothing was wrong with the phone before (and still isn't) it just had a shoddy battery. I know folks with 6 & 6S phones who have A LOT more issues than the battery.
But I falsely assumed that a battery is just a battery. As long as they didn't screw up any other part of the phone, the battery wasn't an issue. If something with the operation of the phone went haywire after this battery replacement, that's not Apple's problem.
There is no problem with the phone. It JUST needed a new battery. I didn't even have any slow downs or lag with the bad battery, the battery life was just crap. My first thought was Apple might consider refunding the difference due to their faulty part, but I obviously didn't think about the fact that once it's been opened by another party, they won't accept responsibility. I didn't get past the part of "Well, they didn't break anything lol.
It's fine, the battery has it's own warranty and it's still in working order. If I break it, I get a new phone. I don't think there was anything defective with this phone beyond the battery so I'll just use it until it wears out.
Using the car shop analogy is good because one should do their research before getting work done to make sure they get the best price. I did not do my due diligence in this case.