OK if we accept you are right which is preferable.
Season 1 100 points earned
End of season x0.5 = 50
Next season earn 100 points total 150
End if season 150 x0.5 = 75
Next season earn 100 points total 175 points
End if season ×0.5 = 87.5 points
Or your method
Season 1 earn 100 points end...