It depends on the turbo size as well. A T3 Super 60 will start building boost by 2000rpms and will be at full boost around 4500rpms or sooner. AFAIK, a supercharger doesn't reach peak boost until redline.
Just my .02
BTW,
here's a JRSC over at focaljet for $1800. (you may have to register to see it)
BP