"But I suppose it's his decision in the end" - it sure is! We must remember that PC World are retailers and as we know some of their staff aren`t as expert as some of the regulars here. It`s nothing to do with ripping people off, you`ll always find something cheaper elsewhere as soon as you buy it.
I buy from PC World and recommend some of my friends to do so when I can`t find what they want cheaper elsewhere. The staff in my local store are very knowledgable and certainly don`t mislead customers. (I wouldn`t know if the graphics card in this instance was up to the mark)
I`m sure the customer in question is very happy with his purchase and if he has any problems he can certainly return to the store to get it sorted out, even if it means upgrading some component. It`s not that easy online is it?