We are aware that we can earn a lot of money in a short period of time, but we believe that sales could hurt some games(especially niche ones like Worldbox) in the long run, since it drops their value. Especially since it's not yet feature complete.
It's also our only project for the next 5+ years, and we want to be careful with it. For us it's not a short sprint where we can move to another game, but a marathon that is slow and steady.
In the future our view on sales could change, but for now we are ok with how things are going.
Also, you can read our reply about the game pricing here:
https://steamcommunity.com/app/1206560/discussions/0/3190239071676925968/