You’re right about colonialism being a net loss for the government. In the Netherlands the NSB (Dutch Nazi Party) based a lot of their messaging around the idea that if the Netherlands were to join up with the allied forces, they would be forced to relinquish their colonies.

This was absolute nonsense but it spoke to people at the time because the idea of giving the colonies their independence had become a popular talking point during the recession because they were no longer profitable (fuckery involving the united fruit company).

During the second world war the Dutch colonies would become profitable but for completely different reasons. Basically a lot of the fosfate used in bombs came from Curacao and the aluminum to craft airplanes came from Suriname.