[apache]

Um, well, regaining initial investments are irrelevant. Remember, whatever resources you do not spend are immediately lost. If you have a surplus of resources every turn, then payback is totally irrelevant since you are not spending anything.
Now, the 150% limit is for generated planets. For example, without modifications, that is the maximum limit of a planet you will find in the quadrant. You will never find a planet with greater percentage unless a value improvement plant has been operated on it, or if you have been using some sort of modification. I do not know if there is a maximum, but if there is, it may be something like 255. I have never reached that on any planet, simply because I have not played a game that long (though I have some saves that certainly could go that long).