Well using this very website to check purchase history, I would make two guesses:
1. Atreu has plenty of gil and can do more than make up for his carelessness. Making a leap here -- he throws around so much gil it doesn't surprise me that he accidentally blew 2.6 Mil or so on a ring worth 1,000 gil. If Isamu used this site he might notice that and hold the gil ransom for at least half of it and if I knew Isamu I wouldn't settle for 600k either lol.
2. Isamu looks more like a mule to me, just a stab in the dark. Like many others, I do most of my AH sales on a mule, if my mule sold a single crystal for 12 Mil nobody would ever know how Pyp got so rich all of the sudden.
And as far as being "nice" and giving it back...lol get serious. After making literally tens of thousands of AH purchases I have no sympathy whatsoever for Atreu. I play on a SuxBox and lag is definitely no excuse in Jeuno, Whitegate or Norg...lol if you blow millions on low level crap by accident it can only be because you're so loaded you have lost the ability to be careful with your gil.