Simple, all I do when someone makes outrageous trade demands is ignore them. If they continue to pester me through pms I kindly tell them what the bvs of the cards are and politely tell them to get lost or something to that effect.
But you have to remember that in the hobby there will be people that always over-value their cards and under-value your cards. You just learn to deal with it. Recently on another site, I was inquiring about an auto patch someone had. He told me it was 2 colors, but demanded a multiplier on it. I told the nimrod that ever since the beginning of time multipliers only apply to swatches more than 2 colors for the most part unless it's a unique 2 color swatch. Fascinating, that he couldn't even provide a scan of the card..