If memory serves, you have to charge a battery to measure this, which takes time and therefore space.
So to get the cost to be cheaper than just building a new pack (possibly using binned new packs), this all has to be pretty automated. If they bin new cells (if they don't maybe they should!), then most of this hardware would already exist. Which would mean you only need to talk about how to make a robot to desolder battery packs. Given how crap my soldering skills are this feels like a potentially hard or at least expensive problem.
Look at the Battery Recycling section.