Chester, you're actually still profiting $250 here. Put it this way: you receive payment from Norted for $250. You now have $500 total (from both clients for t19.) You then refund $250 to the other person who purchased t19, and now you still have $250.

I'm not trying to prove Fjeddy right (because I think he's a smug *****) but you technically aren't losing money, and you're still profiting...

Have you asked the original buyer of t19, if they'd like a new design or something, so you can still possibly retain that $250?