The former Roten star is curious about how the midfielder will fare at his new club, and is unperturbed that the Bavarians were forced to spend bigBayern Munich's big investment to lure Javi Martinez away from Athletic Bilbao.
The Spain international signed a five-year deal with the Bundesliga giants on Wednesday to complete his €40 million [£31.6m] move, despite the likes of Steffen Effenberg to question whether the deal represents value for money.
However, the 66-year-old feels his former club are better off spending cash to improve their squad rather than leave it in a bank account.
"Why would you leave the money on the fixed deposit account, since you hardly get any interest for it anyway," Beckenbauer was quoted as saying by Bild.
"I am very curious about this purchase. It used to be that you only paid so much money for a striker, while defensive players were brought up from the youth system. Times have changed."
Beckenbauer had previously admitted that he had never heard of the 23-year-old, who can play in either midfield or defence.