The magic of the sunk cost is that when you can identify it, you will be able to make a decision more rationally.
Whenever we cough up the money for a recurring sunk cost, we are telling ourselves a story. It may come in many different forms but the gist of it is this:
“This is an investment, and if I stick with it a little longer it’s going to pay off”
It’s an emotional thing. We don’t want to feel stupid and so we keep on finding reasons to keep using our resources.