Monopoly is a zero sum game. So perceiving it as such shouldn't be the bias that leads to poor strategy.
(edit: it seems that it may be possible to play monopoly in a way that generates infinite money and with no win condition)
(edit: it seems that it may be possible to play monopoly in a way that generates infinite money and with no win condition)
What is not zero-sum is the amount of money/points floating in monopoly. If you played a monopoly tournament where players can resign, and at the end of the game you sum up all the money as points for a final ranking you would see monopoly is truly non-zero-sum.