Most people will answer no, and so I like to follow up with a second question.
What if I gave you $10 million dollars for both of your eyes would you do it then?
If they said no to the first $1 million, they are most likely going to say no to the selling of both of their eyes.
(Sometimes, I get someone who says yes they would, I shake my head and say no you wouldn’t, you eyes are precious to you. No one in their right mind would give up their sight for money.)