Pius Minder, who represents Muller, said that the likes of Sir Alex Ferguson and Carlo Ancelotti would have to start the bidding at around the £25 million mark if Bayern were to even consider cashing in on their 20-year-old starlet.
And Minder suggested that the young German forward could have been picked up for as little as £8 million before the tournament in South Africa kicked off last month.
Ancelotti's Blues, who lifted their third Premier League crown at Stamford Bridge in May, are keen to inject more youth into their ageing squad,with Michael Ballack, Joe Cole and Juliano Belletti all axed in the summer.
While Old Trafford chief Ferguson is thought to have become a huge admirer of Muller's qualities following his four-goal haul that has fired Germany to their 11th World Cup semi-final, and could make a move for him to ensure his side is not left relying on the goals of Wayne Rooney in 2010/11.
"Certainly his market value would now have tripled," Minder told reporters. "£8 million? Bayern would not pick up the phone for that amount."
Minder's comments will have irritated Bayern's top brass following chairman Karl-Heinze Rummenigge's comments earlier this week.
Rummenigge emphatically claimed that the Bundesliga champions were not entertaining mega-money offers from United, Chelsea or anyone else for their three German stars – Phillip Lahm, Bastain Schweinsteiger and Muller – who have all shined on the biggest stage for their country.
"If any club should take an approach for any of our players, it would be useless. Our reaction would always be the same. No way, absolutely no way.
"We are not eager to start any negotiation about these players. Muller is a phenomenon."
Muller's sparkling form in South Africa has seen him bag four goals in five games from an advanced role on the right of a three-pronged attack.
But Joachim Low's team will have to make do without him for their semi-final with Spain as the youngster serves a one-match ban for collecting his second booking for handball against Argentina last weekend.
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