Why is the Service Fee for guests this much?

[Lars17]

I was gonna make a special offer for a guest: 600 NOK,- a night for a total of 1200,- NOK.

As it sais on the site:

600kr NOK x 2 nights  1,200kr

Subtotal:                         1,200kr

Service fee                    -41kr NOK

You earn                          1,159kr NOK

AirBnB corrected to Euros for my guest:

"€69 x 2 nights €137

Service fee €23

Your guest will pay €160"

Which suddenly is way more than the original offer.

Is this Service fee correct, and why is it so much? This is something like 17-18%.. Shouldn't it be more like 5-10%? 

Regards,

Lars **