You were smart and packed yourself a sandwich.
This is a 16hour flight, you are 8 hours in and very hungry.
You take out your sandwich ready to eat it.
A man on the plan spots you as you're about to eat your sandwich.
This man offers you money for your sandwich. He insists on having the entire sandwich - not half of it.
How much would this man need to offer you, for you to sell him your sandwich?
Does it make any difference if its a special sandwich (your favourite sandwich, your grandmother made you that sandwich, it was using foreign ingredients that were hard to come by, etc)?