Each time that you collect all fruit in an area of the lab, you will unlock a permanent multiplier. You should try to max out your fruit in the early areas of the lab as much as possible to minimize how much fruit you need later in the game on your way to area 25, and in pursuit of this, you will acquire several permanent multipliers, and before you even hit area 10, you might be starting each run with a multiplier as high as 10x or maybe even higher depending on how devoted you are to 3-fruiting (which sounds so much more ridiculous than 3-starring) every level of an area before moving on. 5mil points is a lot but will come naturally long before you're done with this title.