What does payback time mean?
It is the upgrade cost divided by the extra income earned per minute. A shorter time means the added income recovers the cost sooner.
Compare upgrade cost against the income it adds. Use your own observations, then let the shortest return rise to the top.
Enter costs and income increases you can verify in your own game. Nothing is prefilled.
Add a valid cost and positive income increase to compare payback times.
It is the upgrade cost divided by the extra income earned per minute. A shorter time means the added income recovers the cost sooner.
The income increase must be greater than zero. Blank, zero, or negative increases cannot produce a useful payback time.