Glazing question.

A few months ago I phoned a glazier for a price of a piece of TOUGHENED 6mm glass 24"x36". He said £13 +vat.
On collecting the glass he saw it was for a company and when he sent the bill it was for £37.75+vat. When asked why the difference he said he didn't realise I wanted toughened.

What kind of price should I/the company have paid for the glass? A rough estimate will suffice because it is just for my own curiosity not to make a claim or anything.

Thanks in anticipation.

I had a piece of toughened glass for a table top, about that size, was about £35 I think, for 4mm thick and bevelled edges so for 6mm it sounds about right to me.

Thanks FM, sorry I haven't got back before now but been away on a course and only finished earlier today.

This was just for my own curiosity.