Hey David,
While there isn’t a way to add a dollar value to options, you could certainly use Event Tickets Plus’ “Attendee Meta” features to add things like T-Shirt choices and sizes to a ticket. This information is visible in the attendees list after checkout and all of that.
To learn more about these features, first update your site’s versions of Event Tickets and Event Tickets Plus to the most recent version (your System Information shows that you’re running version 4.1.3 of Event Tickets Plus; the current version is 4.2.3).
Then, read about attendee meta (AKA “Additional Information”) here:
• https://theeventscalendar.com/knowledgebase/managing-your-orders-and-attendees/#attendee-info
• https://theeventscalendar.com/knowledgebase/collecting-attendee-information/
As mentioned, there is not currently any support for having these meta choices alter the cart price or ticket price; nor can you have options that themselves cost an extra fee or something. But I hope this information helps nonetheless.
Cheers,
George