My Bloons score is after completing the game with, iirc, only two bloons getting past. Since I didn't get a perfect score, there's still potential for someone to beat me.
The biggest score boost comes from economy - buy only the items/upgrades you
need to pass each level, so you can get your super monkey out asap.
It's a bit unfair in some ways, I'll admit. I played all three Bloons games and the super monkey game like mad a long time before they were added to Kokaro. I love Tower Defense.
(Except that Toytown one. The combo system is broken and I don't like moving towers.)