Ok...just to clarify.

The item was $42 and quoted postage was $15 = $57

It actually cost me $27.15 to post because of the buyers location and size, so I'm out of pocked $12.15.

Buyer said it's faulty - I have completely refunded the $57 to them.

My question is 'do I pay for the postage back'?  I know how much it costs and all money to the buyer was refunded but I know it costs more to post it back.

See my dilema?

Depending on what the buyer tells me, it could be $30 to post back, so do I have to pay the $30 or just the difference as all their money has been refeunded to them.

I want to do the right thing, hence the question.