Second-placed Real Madrid boast a higher operating profit at £56million but lag behind the Old Trafford club, for whom Malcolm Glazer paid £0.7billion in 2005.
United's domestic rivals Liverpool have put a season of boardroom strife behind them to rocket seven places from 11th to fourth place in the list.
The Reds' value more than doubled from £227million to £525million despite the ongoing controversy over the club's ownership.