When did you get the quote? It's cheaper if you do it during the last 30 days, if you do it before it will be more and if it runs out and then you do it add about 50% onto the price!
I'll be getting it for my A5 @ £250 excess = £297.43 so it's not even £1 a day for piece of mind, if the s-tronic went bang you are talking thousands!