What's the value of?...

[jellyroll]

Hi, I wondered if you could help me. I received this Halo 3 limited edition poster that is autographed by Chris Carney and Joseph Tung.

I wanted to find out how much it was worth and I thought maybe some of the people here might be able to give me a ballpark figure.

Here are the links to some photos of the poster and certificate of authenticity.
Thanks very much!

http://imgur.com/a/kXjQC

http://imgur.com/a/FNdQ6

http://imgur.com/a/wXYRy