That’s alright. The reason it is priced so high is due to it being an event item that is unobtainable today. So as the day’s go on its value rises even with it being a vanity item. Don’t know if that makes any sense, but you’ll see why soon.
General rule of thumb is that If you’re looking for a Headless Head, you should be willing to give a Swift/Clean (Unenchanted) Sunken Sword with no other additional items, or 4-5+ sunken pieces depending on the piece and trader.
For more in-depth values, check out the values list from MrNormalBox, and try checking around the forums to see what other trades may trade for the item you’re looking for.