I have a Tenchi Muyo manga signed by the director of the Tenchi Muyo anime. Totally unrelated (he didn't make the manga) and it's probably still worthless.
Point of this anecdote is all you have to do is go to a convention and be patient. Signatures aren't hard to get.
+1'd for truth. I have a poster of the cast of Dragonball Z signed by the complete main English cast locked away somewhere. That cost me $75 for convention admission, $12 for the poster, and 6 total hours of waiting in various lines
And even with those signatures, the poster wouldn't be worth $87 if I tried to sell it.
I'd be lucky to get the customer to pay $15, including shipping, for that sort of thing.
I guess what I'm trying to say is that... yeah. I agree with y'all. Auction's a rip-off.