To clarify: Sonne, of course, does not have to pay to attend her own preliminary test. However, the test is an event at the very end of TAM on Sunday. TAM would not be free to her, and she is still paying the cost of materials.
Also, the Penn & Teller performance is an optional item and costs extra.
Sonne is paying her own expenses to get to Las Vegas, and is paying her own hotel fees. She wanted to come to the US to take her test, so this is not the equivalent of inviting a speaker from Denmark and not waiving registration.
As for mingling with the skeptics, though....
Immediately following the test is a press conference with Sonne, Banachek, Randi, and possibly me (I'm not really sure where I'll be needed just then). The press conference is invitation only, and the guest list has 64 heads of skeptical organizations, podcasters, media representatives, magicians, and more. Penn & Teller are included on that list.
Sonne will take questions from all those folks.