One of Carlo Ancelotti's alleged priorities on his return to the Bernabeu is to reduce the age of his central midfield options.
In recent weeks, it has been suggested that 25-year-old Merino has emerged as a potential transfer target having impressed in La Liga over the past 12 months.
However, according to OK Diario, Sociedad have informed their Madrid counterparts that Merino will not be sold for less than £51m.
At a time when Los Blancos must reduce their outgoings, paying that amount of money for a player who did not make Spain's Euro 2020 squad appears unlikely.
Merino still has four years remaining on his contract, putting Sociedad in a strong position with regards to his future.