Hey Glenn,
Thank you for reaching out to us!
Event Tickets Plus does allow you to set the price for your tickets to be anything you would like. However, it is a single price field so, if you are planning to add in a service fee, then it would need to be added in with the original price. Unfortunately, the plugin will not line item both costs.
What is your eCommerce plugin? If you are using WooCommerce, to get started, I would recommend you to check the following article (it explains how to configure fees/surcharges for your products ):
Add a surcharge to cart and checkout – uses fees API
Does this help answer your question? Please let me know.
Thanks,