According to this Flyertalk thread, Singapore Airlines appears to have filed a bunch of full (Y) and nearly full (B) fares between the US and various citieis around the world for less than the cost of discount coach inventory. Clearly a mistake. For example, New York-JFK to Frankfurt roundtrip for about $800, refundable.

The nice thing about these fares is that — provided you can find upgrade inventory — these fares should be upgradeable with miles from most Star Alliance programs. And that many Star Alliance programs offer bonus miles for flying on such tickets.

The trick of course is Singapore upgrade inventory. But a heads up for those interested in reading the Flyertalk thread, nonetheless.