The Lieutenant Guard Sashes (the ones with +2 Mana Regeneration) have sold for up to 1.8 billion gold. As for being able to legitimately collect that much gold in UO it is entirely possible. When character transfers first opened our guild sold over 1 billion worth of power/stat scrolls in a couple weeks.

As a recent LLTS interview pointed out, the same effort expended to put together a measly 10k 10 years ago could earn someone millions today. If I played like I did back in 2000 I could easily pull in hundreds of millions every month. If you work hard at it the gold will come.