17. Manchester United
Manchester United have surprisingly made only one sale in excess of £6.6 million in the period under analysis by Football Observatory, with that of Cristiano Ronaldo for a then world record fee.
Ronaldo joined Real Madrid in the summer transfer window of 2009 for a fee in the region of £80 million, making him the most expensive Manchester United sale by some distance indeed.
David Beckham joined the same team for £25 million some six years earlier - a sale not counted in the analysis - and these two are the only two to have departed for fees in excess of £20 million.