There is another way. Irrationality. People spend a lot on religion. Like a whole lot.

What if there was a faith system of ultimatley going to interstellar medium. You have faith, you automatically pay, like the rest of the people and you dont question it. You get tax breaks. It will help you in the end of times or something.

Just decide the ultimate goal to be interstellar medium touching in all directions.

You are a farmer? Well now you continue to farm to feed budding spacers. You are a game dev? Well, people are going to get bored in space, continue developing games for the ultimate goal.