Quite the contrary, they cost us an enormous amount - between the costs of fighting them, the fees that get attached to stolen cards used - and all the ill will from players.
And just because we fight them, doesn’t mean they don’t come back. We do banwaves in the hundreds and thousands at a time. Within 2 days, or less, they come back - but we don’t stop fighting them, we continue to fight them.
As I said, until there is no longer a financial motivation to do so, these will never go away and that is 100% fully in the hands of players that give them money.