I've seen one of Redline's Servals on the dyno personally. It was 85hp with an awesome curve. That was ported. That same exact motor and setup made right around 77hp before porting. This is a pump gas motor.
These 4mm Servals aren't rocket science. They're doing exactly what they're supposed to do.
I talked to Cameron last night about them. He said it's roughly 10hp from no porting to porting.
As far as price is concerned, I don't know what Redline or anyone else charges and don't really care, but if you're getting an extra 10hp for $250-500 you're getting a good deal as far as I'm concerned.