That deal was a sodding great bung to Mendes, probably to ensure that we got first dibs on his players in the future, such as De Gea and Garay (if we had wanted him). It can comfortably be ignored in terms of relevance to what we pay for our players.
This, it could simply not have been anything else. I'm almost shocked we didn't get fecked over because of it. Not that I mind though.