I contacted ebay and was told that this is a scam. When you get a tradmark violation they cannot demand money from you they can only remove the listing. He also said that anybody getting a email wanting money from you should be forward to spoof AT ebay.com.
Ebay has had several other members...
I received the same letter from this Stacy Papachrstos,Esq. wanting $500 for a Voltron shirt that I made and sold on ebay. The thing is that it said that she represented Classic Media Trademarks. I did some checking and Classic Media sold all there trademarks to Dream Works in Feburary 2012.