When a player leaves Rangers the club may make a profit on the deal. If the player is sold for more than their book value it is a profit, for less a loss.
Teams like Hibs live off nurturing and selling on young players which makes them instant profits. Rangers have not generally sold off young players, and have also kept players to the end of their contracts and got little when selling them on.
The big boost in 2008 came from the sale of Hutton and Sebo, in 2009 mainly from the sale of Cuellar.
The 2010 results will show money in from the sales of Ferguson and Adam.
It has to be emphasised that the club made a loss of over £12m despite making £6m profit on player sales!!
Rangers - Player Trading