Just to throw this out there, it's not going for 400$. Some dick is trying to sell it for 400$ dollars. That shirt has 0 bids.
There's one right below it for 102$ with 16 bids. One is at 31$ going for a buy now price at 300$.
I'd actually say....hang on to it...unless you want a cheep 50-100$, no way you'll get anyone to buy it for more than that.
EDIT: But then again, 100 bucks would be some nice money to your pocket when you can buy the shirt on WWE.com for 25 bucks later. WWE would be stupid not to start selling those shirts...all though they might even make the prices a little high at first, but not 100 dollars high.