@asto-willzz Hi, welcome.
Crew duels are special leagues with special schedual and with different winner> group of managers instead of individual manager.
So yes, on duels we allow that managers help their crewmates by selling their weak players at lower rates.
Both crews can do the same, so no one will have any unfair advantage over his opponent.
On normal leagues, this is not possible neither allowed because it's pretty much impossible to keep it fair to all managers on the game.