#2 Clubs wait to sell so that price is driven up by WC performances
When it comes to selling a player, the economic considerations are very important. Especially, of course, when it comes to want-away players. Arsenal’s hardline stance regarding Alexis Sanchez is backed up by the simple economics that the profit they would generate if he propels them back to Champions League would far exceed any transfer fee he would currently fetch.
Similarly, clubs are tempted to hold on to their precious assets for at least a year more, with an eye to the upcoming World Cup. Players like Mesut Ozil and Keylor Navas are poster boys for how a good World Cup can be the making of your career.
If a player can fetch a higher transfer fee next summer than this summer plus inflation, why would you sell the player, unbalance your first team and risk tedious efforts to find a replacement?