You can change the commission fee by contacting us with the support tab within your admin portal or please submit a ticket.
You can submit a ticket by clicking on the link here.
It is really important that you tell us your:
1. Marketplace URL
2. Your admin login ID (this could be your google or facebook openID email or your custom login)
3. The new commission fee you would like to have
Arcadier will make these changes for you.