Amazon Marketplace - an odd update

This can't be right? Should used books be more expensive that new ones? Or is it something obvious I'm missing here.

When I searched for Elementary Fluid Dynamics it said the price new was £25.50 but that I could buy it used for £25.94. Ok, the book this seller sells is "Absolutely New - Never Been Read" but still.

What are his chances of selling his "used" book when his price is higher than that of Amazon?

One potential benefit is if Amazon is out of stock and the seller has one available.