So you spent nothing, have been payed back in full and you have the shippers property and he is out of pocket for both shipping fee and the item.
So just what high ground are you on again? What is the lesson you want to teach him.
Whatever you think it is or whatever your reasoning now... it doesn' t really fly alongside the virtuous mud being applied here. I'm betting the cost to send it would be negligible to pay it in full.
Your withholding his property unpaid for by you for the sake of a few bucks (his half ?) and some idiotic moral dilemma... its literally a few bucks out of your pocket..compared to his loss...regardless of how anything is packed the delivery "experts" will always find a way to damage things.
My conscience would be clear when he had his property back .
but I'd never post this type of stuff on a forum about a private sale. Personal escalation in mass never works, feedback after private discussion is usually sufficient and less likely to have one of two ignored afterward.
That's just how I see it...
Apparently....