Excluding them didn't devalue anything, nobody would pay money for these players. Everyone in the world saw how they played against Mura and Morecambe last season. Excluding them was the best thing to do because it sent a clear message to them that they will not play for this club again.
Nobody outside of England has any money anyway. Pepe left Woolwich on loan, Dele left Everton on loan, Hudson-Odoi left Chelsea on loan, continental clubs cannot afford to pay a nice fee and take on the salary of these players as well.