Is a fair exchange no robbery if one side is getting hosed?

A college kid has a 1968 Chevelle SS Super Sport but it is pretty rough. The kid got it as a project figuring on making a really cool retro ride. But there was more wrong with it than he thought and his college cost had gone up so he thought to cash out of the car. It is said he was going to place it on Craigslist for $2,100. An elderly man in the neighborhood having dreams of nostalgia hears the kid is going to sell but not the price. When he lets the kid know his intentions the kid says he will sell it to him for $8,000. They say fair trade is no robbery if the old man wants it that bad I guess the price would be worth it. Would you say the kid is trying to hose the old guy because he figured he could get no better than 2k and change off CL but because he knows the old man has money but far from wealthy, and loves the car he can squeeze him for more money. Do you think it is ethical? Would