So VMF - what would you do?
Well, you asked.
If you keep it, it's theft.
There, I said it. You hold a legal trump card but it doesn't change the moral implications of the deal.
No, I don't believe in "Karma" BS. There is no force in the universe that gives a rat's pitoot if I steal something and will plan to smote me if I do wrong. I'm just not that important. But I know my dad would say it's stealing and he raised me well.
TBH, I don't even know if I could take the 50% deal as I know they paid more for the item than they sold it to me for.
EDIT: I posted this after reading the first few posts and was so worked up, so I replied before reading all the other replies, and now see that you're considering other options. I hope you do what you know is right.