If you want to change who covers your fees, you'll want to go into editing your page, then open up the sidebar.
Afterwards, select the Fees shown below:
You can control how donation and ticket fees are handled:
If you'd like the attendee/purchaser/donor to cover your fees, select Purchaser.
If you'd like to absorb the fees yourself, select You.
If you'd like to let the attendee/purchaser decide, select Optional.
Once you're done, don't forget to press Publish Changes at the top right -- that way your changes reflect on your live page.