Is it more cost-effective to "replace the battery" or "buy new" for degraded AirPods?

The batteries in AirPods are consumable, and with daily use, their perceived longevity decreases over 2 to 3 years. Apple does not "disassemble and replace" AirPods but instead offers "replacement units" for each side or the case (known as battery service). If you have AppleCare+ and the battery capacity is below 80%, the replacement is free; otherwise, there is a charge. In Japan, at authorized service centers (e.g., Bic Camera), the guideline for out-of-warranty battery replacement is approximately 7,900 yen per side (for AirPods/Pro 1st and 2nd generation), totaling about 15,800 yen for both ears, with an additional cost for the case if needed (prices may vary by store). Meanwhile, as of 2025, the prices for new models are: AirPods 4 (standard version) at 21,800 yen, AirPods 4 (with ANC) at 29,800 yen, and AirPods Pro 3 at 39,800 yen (all prices include tax). Therefore, the "cost of replacing both ear batteries ≈ the difference with a lower-tier new model" becomes a point of comparison. Considering functional advancements, warranty, future value, and market trends, it is generally more advantageous to replace standard AirPods, while for AirPods Pro, the decision depends on the symptoms and usage. This article organizes the "optimal solution" from the perspectives of cost, functionality, risk, and environmental impact.