Your question was probably rhetorical -
The list may need to be updated, but yah, isk sinks are pretty much npc related, fees, taxes, etc…
From 2012, player Tippia: Faucets: NPC bounties NPC buy orders Agent rewards: Mission rewards, Mission time bonuses, Incursion rewards Insurance payout GM actions: Reimbursement for lost pods Character creation Sinks: Market taxes & fees: Broker fees, Sales tax NPC sell orders NPC station services: Repairs, Jump clone installation, Medical clone installation/upgrade/station change, Science and industry slot rental, Ship insurance NPC station office fees: Rent, Impound penalties Wardecs Sov…