These Milwaukee, DeWalt, and Ryobi batteries all say 5Ah, but one costs way more

Walk around Home Depot’s battery aisle, and three packs share one peg. All three read 18V. Two carry a 5Ah stamp. You’d expect the third to match. It doesn’t even try. Ryobi never put a 5Ah pack on US shelves, and that missing number is your first hint that the figure on the front sells the battery more than it measures it.