Mad World said:
Profits aren't everything; they owe their fans a finished story.
No, they don't. They do not owe people a game.
Saying that they do is the very definition of entitlement. It's also not even what the word "owe" means.
If they had taken orders for the next game or charged people for three episodes when selling HL2Ep2&3 then yes, they would owe people. If they had announced the next game then you could kiiiiinda say they owe it to people to release it, but that's already a stretch.
But they did neither of those things.