My understanding is that Sporting paid €4m + 20% of any fee received for him above €4m. With Doyen owning 75% of Rojo, a €15m buy would result in: Doyen gets 11.25m, Spartak gets 2.2m, Sporting gets 5.95m. Given that they inintially paid 4m for him, their gain will be around €2m for a player who's now a starter in the Argentinian national team, which off course is not a good deal from their point of view.
An even better deal was made by our previous President regarding Carvalho. He sold 40% for 400k to a fund (that has people connected to him in it). Now they will probably get more than 10 million euros for that. It was this kind of people that almost destroyed my club. Have no simpathy for this mafia and i hope they are completely screwed.