I sold a Phase Eight cardigan for £20 on Ebay last week. The buyer has messaged today to say that one of the gemstones from the buttons is missing. I of course apologised immediately as I hadn't noticed this, and offered her the choice of a partial refund of £5 to enable her to try to find a replacement button (or suggesting that she might move the top button down as my Granny would have done 
) , or a full refund if she preferred (as she seemed to want to keep the cardigan).
She has replied saying that she'd like £7 as buttons cost £1 each.
I have said 'then please send it back and I will refund you in full'
I feel that she's taking the wotsit a bit!