Mate you do realise that Athletico are in a huge financial hole, with debt at about 500m quid atm and debt loan repayments of 17m quid a year, also the way Spain works with tax on transfer fees takes a shed load off any player sales too
Spent 31m last year sold 70m 2013 -39m net spend
Spent 4m sold 18m 2012 -14m net spend
spent 80m sold 75m 2011 5m net spend
Spent 29m sold 21m 2010 8m net spend
those figures show a spiralling crisis for them financially and one alluded to by their president the other month, the champions league may stop it getting any worse but their still set for a big net spend again this season, selling Costa isn't about them going out and splashing 20-25m to replace him they need to sell to survive mate, and Lukaku will probably be out of their price range unless they have some other major sales on top of Costa
theirs a reason remember why they couldn't actually afford to pay the 5m to be able to play their keeper against chelsea until Uefa saved them with their competition ruling