Ferguson said that given Real's willingness to pay £85m for Tottenham's Gareth Bale, he believes that the Spanish giants would have happily paid £150m for Ronaldo.
He is quoted in AS as saying: "I told David Gill to ask for £150m. Perez would have paid.
"The only thing that hurt me, and I said this repeatedly to David Gill, was that we didn't demand enough.
"I told David, 'Ask for £150m'.
"He said, 'Don't be silly. They'll never pay £150m'.
"I said, 'Ask for it because he's worth it'.
"We signed the deal. I think it cost £80m or so but I'll always wonder what Mr Perez would have said if we'd asked for £150m."
For breaking stories and all the great banter like us on Facebook: facebook.com/tribalfootball