I got the Disgaea items autographed when I attended a press event held by NISA in San Francisco in 2008. The newsletter was being passed out there. I had a silver pen with me and I went up to each of the staff and got autographs.
The Darkstalkers poster was given to me by an employee of Capcom in appreciation of the work I did on the instruction manual for the game.
I will consider lower offers on the Joust poster. It's hard to value that one. After trying to find some recent sales history and finding none to go by, I have to base my price on rarity, condition, subject matter, and aesthetics. I think this one scores very high in all of those categories. However, I may have priced it too high. So I'm putting it on eBay to let that market have a go on it. If you make an offer I am happy with and there are no bids yet, I will pull it off eBay to sell it to you here.