Again, the only way to really combat this is to remove the demand that's bringing the bots in.

The moment SE decides to do their own method of facilitating gil transfers between players (like how Blizzard did with their WoW token)...99% of the bots go away, probably overnight even.

The only other solutions are to keep doing what they're doing (which obviously doesn't work), or try banning players too (which [a] would be hard to prove and could lead to griefing and [b] still might not work and [c] would absolutely have a negative impact on their subscription growth)...or ignore the problem (which also wouldn't work).