I was told some years ago by a friend in engineering that higher spec ABEC bearings were only a few quid difference - around a tenner at the time, probably fifteen quid now..

I loved using the 309 and series V though. The M-2 series are apparently very good too for most purposes. Remember, the series V has been out since the mid eighties at least and tooling costs should have been written off many years ago. What's left is pure profit I reckon..