Joe Gladstone, Assistant Professor at UCL School of Management, has been discussing how companies price goods on BBC World News.

In the run up to Christmas, companies and shops offer products at greatly different prices.

So much so that it can cost you significantly more to buy smaller packets of chocolate, for example, than a bigger bag or box.

In his interview, Joe talks about why retailers price items the way they do, insisting it's not always about the cost of producing the product.