The battery is a user changeable part on most mid-range and low end phones.
The point of this predatory pricing tactic is to force owners of phones with sub-$200 in value to upgrade, rather than potentially waste half (or more) of the phone's value on replacing the battery.
Which carrier sold Android phones - where most users by their phones - have user replaceable batteries?
The Moto G is usually cited as one of the best mid range phone and it doesn’t have user replaceable batteries. I don’t think most of the cheap Walmart phones have user replaceable batteries.
The point of this predatory pricing tactic is to force owners of phones with sub-$200 in value to upgrade, rather than potentially waste half (or more) of the phone's value on replacing the battery.