EDIT - When looking up Watch service prices I missed that there was a cheaper $80 battery replacement vs the general out of warranty service price. But that's still 47% of the current street price (S3 is $170 from Amazon, Target, or Walmart).
Similarly, AirPods are $50 each for battery replacement, another $50 for the charging case, versus a list price of $200 and having gone on sale for $150. So if your batteries are shot in both AirPods and the case it's 75% of list price, or the entire full cost of buying them on sale. And this is a device where when brand new the tiny little batteries were barely good enough.
If my car's transmission blew and it was $10,000 to get it repaired, I'd be taking it to a scrapyard instead of a mechanic. Same goes for a 2-3 year old gadget if I'm expected to spend 75% of the replacement cost to get a battery replaced. I'm just going to say "I guess it's time for an upgrade" and see if someone on CraigsList will pay me for the old one, maybe just for spare parts depending on how bad the battery is.
If Apple really wants to extend the lifetime of their devices, they need to get the price down for replacing the disposable components, or make the disposable parts user replaceable again.
I've said it before re: AirPods battery life, but this was a predictable outcome for something with a 5 hour battery: https://9to5mac.com/2019/01/28/airpods-battery-life/