Always premium fuel in all motorcycles. The higher anti-knock compound makes it run cooler which is better for the motor.
My head pipes were turning a nice golden color and after few thousand miles I discovered the motor is rated for low octane so I filled it up with regular. The tops of the pipes and collector then turned blue...I was a little pissed. So no more for me, always premium.
And anything with titanium valves will last WAY longer on premium, even a shot of race gas if you can manage it. I think the XC has steel valves, but will run cooler nonetheless.
I really don't think a bike is cheaper to run than a car except for the gas.