The switch, which makes McCormack the eighth most expensive British striker of all time, underlines the huge sums that are involved in signing domestic players, and has been held up as proof that the current transfer market is vastly overinflated.
Middlesbrough have tracked 27-year-old McCormack for the best part of two years, and made a number of attempts to prise him from Elland Road last summer.
Tony Mowbray tabled four separate bids for the Scotsman, with his final offer worth around £2m, but all were rejected by Leeds chiefs.
McCormack went on to score 29 Championship goals last season, and while Boro’s interest remained intact despite Mowbray’s departure and the appointment of Aitor Karanka, it became clear at an early stage of this summer’s negotiations that the Teessiders were going to be unable to pull off a deal.
Newcastle officials made inquiries of their own earlier this summer, with Leeds owner Massimo Cellino claiming he had turned down a formal offer from St James’ Park.
Senior Magpies sources dispute this, but the club would have been interested had McCormack been priced around the £6m mark.
As it was, Fulham’s interest rapidly drove the striker’s price towards eight figures, a sum Newcastle’s recruitment team believe is way too high given McCormack’s complete lack of experience in the top-flight.
The striker, who signed a new four-year deal at Elland Road last summer, told Cellino he wanted to leave in a face-to-face meeting last month, and was left out of the Leeds squad that travelled to Italy for a training camp.
He is Fulham’s fifth summer signing despite their relegation at the end of last season, with the club’s flamboyant owner, Shahid Khan, clearly determined to back Felix Magath’s attempts to win promotion back to the top-flight at the first time of asking.