Is Shark considered a "high end" helmet?
I've tried on every helmet out there and every Arai, Shoei, and Suomy fit all to no avail. HJC's fit me perfectly (unfortunately) so I've always stuck with them, and they've done me well.
A few of my racer friends suggested Scorpion's after having the same issues as me, and they've had no complaints and crashed in them.