Euro Tunnel Prices

[Been]

Firstly I want to say that I had a brilliant first time at lemans! However my car broke down on the friday and was towed to a garage to be told it would not be repaired until next week (Thanks to my french friend who was on call to translate over the phone!). It was quite funny being heckled by everyone in Arnage on mad friday as we were sheepishly sat in the front of a tow truck.

As a result I need to go back to lemans next week to collect it. Looking at euro tunnel prices, a single fair is more expensive than a return and I can't understand the logic. Will I be penalised for buying a return from calais but not returning?

Thanks for any Enlightenment!