Until this happens a few times and their algorithm flags you as an 'abuser' of the refund system (despite you doing nothing besides correctly calling out fraud) and you're banned or automatically ruled against in all disputes going forward.
But in this case they ended up with no product, the same starting money and a bunch of time/energy lost.
They ended up with twice the amount of money and some time wasted.
> We got a refund from the seller pretty quickly and they told us to keep them.
So they made some? Spent time/energy for science of course ...
The way I read it they ended up with double the starting money, because they both got a refund and sold the headphones.