When I'm dealing with someone like this, I've got no problem with telling him, "The bike you're offering me, once it's cleaned up, new tyres and chain, and everything regreased and adjusted will sell for $125.00. I'll put in roughly 20 hours to get the bike that way. Which means, my total purchase budget for bike and parts is $62.50. A chain's going to cost me $5.00, tyres will be between $10 and $12 each. Which means I've got roughly $37.50 left to purchase your bike."

A few come around when hit like that, most (of course) will, "fix up the bike themselves' and get the whole $125.00". It all depends on whether I'm dealing with someone who can pick up a couple of bucks for something they were going to toss out anyway, or, someone who really believes they've got Sutter's Mill in the back of that pickup.