Reports in the British media on Monday morning suggested United are prepared to pay the Germany international £250,000 a week if he moves to Old Trafford.
Kroos would treble his wages if he moved to United, who would reportedly be prepared to pay the German giants £30m for his services.
The midfielder's contract ends in June next year but Bayern have as yet been unable to agree a new deal with the 24-year-old.
Bayern's honorary president Beckenbauer told Sky Germany: "He shouldn't raise the stakes too high.
"Bayern will make an effort to keep him, but when the demands are too high, a decision will be made.
"There is no player who you have to give everything to keep. Everyone is replaceable."
Bayern's director of sport Matthias Sammer says the European champions are keen to keep the attacking midfielder.
"We know that he is a very good player and we want to continue with Kroos," said Sammer. "Everyone at the club sees it that way."