Go to :
C:\Program Files (x86)\Steam\steamapps\workshop\content\32470\1770851727\Data\Xml
and change the file with planets written on it.
Another way to upgrade your income would be to change how much money some buildings give you, which wouldn't make the game too easy for you. Go to :
C:\Program Files (x86)\Steam\steamapps\workshop\content\32470\1770851727\Data\Xml\Buildings
and select which buildings income you want to change (in the space or ground folder).