The former Bayern Munich manager believes it is unjust that a club can spend so much on new players while harbouring such heavy debt.
"[Bale's signing] is incomprehensible. I do not understand how you have so much debt," he told Futbol Tactico. "It seems unfair that Madrid can buy these players with the amount of debt that they have. It's not fair."
Los Blancos spent £152.7m strengthening their squad over the summer, while the club's debt amounts to more than half a billion euros.