And everyone makes enough money that something going wrong with their €1600 payment/expectation isn't going to ruin relationships.

It might not actually be "buy one-another new cars" territory, it's closer to that than paying for your friend's coffee or buying an appetizer for the whole table.

Why can't renters plug a battery into their socket, too? As long as the electric house grid is rated for the specified power (might not be the case on some countries, or in extremely old homes).