You can change the price for an event and sub-event.
When you login into your race menu account racemenu.com and go to manage my events and choose the event you want to edit. Click on the manage button:
At the top of the page, you will see a toolbar click on sub-events and from there click all sub-events.
You will see your races listed and to the right is an edit button, click on that.
If you scroll down the page you will see an add fee change button. Click on that and update the event to reflect the new price or schedule it out. After you have done that click the green save button at the bottom of the page and you are finished.