Events Tickets Profit for the comany
If you're looking for a pct fee on top of your order, you've got a couple of options, the quick and dirty one is to create a fake tax of the percentage you want, see http://www.drupalcommerce.org/user-guide/tax-configuration, another option is to multiply the amount by 0.15 or whatever quantity on the rules event you choose. 

For fixed fees you can check Commerce Fees

You've got also commerce discount and commerce coupon that do the exact opposite operation, so you can check how to add and modify stuff in the checkout, if you're looking for a more advanced solution.