BBC Top Gear’s Jeremy Clarkson claims petrol at a pound a litre is cheap compared with…for instance, bull semen at £24,000 a litre.

He maybe right but is he comparing apples with pears, so to speak?

So how do you compare the price of things?

FW’s online editor, Julian Gairdner, asks exactly that question on our Food for Thought blog. Why not take a look and answer his poser?