No madflo you would need to spend much much more than that. What you are trying to do is assume that raising a level is linear in effort across all star levels. That's why you assumed that if one star cost you 30, then 4 would equal to 120 and that's too simplistic for how the game is.
The star levels get increasingly resistant to training the higher up you go and depends upon many factors including quality of player, age, and how many stars you go up.
So while we all wish it was that easy, it isn't, and you haven't tried it except for one star anyway which makes me think its because it started feeling harder to power up