Alexis + cash (15-20m) makes more sense than Cesc+cash for Aguero.
Also, Cesc+38m would be a horrible deal, even worse than 46m+Eto'o for Ibra!
btw according to transfermarkt, Aguero is worth 50m, Cesc 55m, Alexis 33m euros. Which are logical numbers, maybe Aguero is wortha bit more, but if...