Build points are more scalable at the lower end than karmagen, but at the higher end, you need to start adding additional things to it - such as higher Availability, more that can be spent on gear, and so on. Otherwise, you will have a disproportionate number of awakened characters. They will get everything they want and have points left over, so they will go "Hey, I'll make this guy an adept."
Most high-level games with prime runners use 400-500 build points, then add some karma on top of that. This lets the players do things like initiations, raising additional skills to 5 or 6, and so on. Because going over 500 points, you are typically creating upper echelon runners.