People still dont understand it's entirely for spanish financial fair play reasons.
Just an example to understand it:
If you sign a 5 year contract with a new player for €70m transfer fee and €20m wages, you have to devide the complete cost over the contract's lenght to know his yearly costs. In this example, it would be 170 (€100m in wages + €70m transfer fee)/5= €34m/year. The spanish ffp writes those €34m down as the clubs new yearly liabilities.
If you sell now a player for €70m and €20m wages, you instantly get €70m and save €20m in wages. That's €90m in total for this financial year.
Although financially speaking both players cost the same, you freed up €56m in ffp space for this year.
You see the difference? That's also the reason, why Bartomeu did those shady exchange deals with Valencia and Juventus (Cillessen and Neto, Arthur and Pjanic). You sell a player, the whole sum counts as income. You buy a player, you divide his cost over 5 years. So no, it's primarily not about wages or same transfer fees, but to free up space in the ffp.