Seems to me that the value proposition is a matter of perspective; your particular rationale for choosing to replace a battery in your 12 mini wouldn’t match up to why I recently replaced a battery.

We were looking into switching carriers and part of that was going to be taking advantage of a promotion to get deep discounts on new iPhone 14 handsets for everybody in the family – assuming that we traded in our existing handsets, of course. (That’s how they lock you in… it’s much harder to leave if you don’t even have your old phone anymore – but I digress.)

Well, my eldest daughter’s iPhone X Plus in particular was getting pretty long in the tooth, and it showed in the battery health. When we looked at the numbers, we found out that if we replaced the battery in her old X+, it more than doubled the trade-in value of that phone… even though the cost for a battery replacement was well below that. So I took her phone to a local shop, had them replace the battery and shipped the newly refurbished phone off to the carrier. So was it “worth it” from my point of view? Aw, heck yeah.

In your case, I would assume that you’re looking to actually use your iPhone 12 mini, after replacing the battery. Would it be worth it to you? Honestly, I suspect the answer is still yes, but for a different set of reasons. If you have a particular affinity for your mini, possibly because you just can’t abide the larger form factors, then you’re pretty much stuck with a 12 or 13 model, as there is no 14 mini and there almost certainly won’t be a 15 mini; Apple has moved on from the smaller form factors. And given that an upgrade to a 13 would be a lot more money for a lot less relative value, I personally think you might reasonably find it worth the few dollars that it would cost to replace that battery.

Oh… but don’t do it through Apple; do it through a reputable third-party. Way less expensive, and likely a lot faster. (In my case, it took about an hour.)