I know things get damaged in the post. When a buyer claims that to me, I ask for photos of the broken goods and the packaging - especially for such a trivial amount.
If I can see the goods are clearly damaged I refund the buyer and claim the value from the post office - the contract is with me as I posted the goods, it is my responsibility to claim the refund.
As a seller it is my responsibility to ensure the goods arrive in good condition. If they are lost or damaged in the post, the buyer should never lose out a penny.