The Mirror says United boss Sir Alex Ferguson and the club's money men believe this is the magic number that would make the move happen and are prepared for an official offer in the next few days.
United won't sell Ronaldo for anything less than a top price, but they accept business could be done if Real Madrid president Florentino Perez can back up his dream with cash. Perez publicly announced in Spain yesterday that Ronaldo is his next target, to play alongside Kaka.
Ferguson knows a £75m fee is good value and it would give him the funds to sign two or three players. United have not raised the subject with Ronaldo, who has been on holiday before joining the Portugal squad for their World Cup qualifier away to Albania.
However, Ferguson has told friends in the game that £75m is the level that would make United take Real seriously and see the Reds star head for Spain.