A big part of this and the Nunez deal is probably the wages.
Sadio has reportedly asked for an increase from 120k to around 400k, supposedly agreeing 320k, 16m per year with Bayern. If we gave him that, that's an extra 10mill per year in wages.
Nunez, according to reports has agreed to 120k for the next 5 years.
So buying Nunez, even for the 85m seems like roughly the same money as extending sadio would cost when you factor in selling sadio for around 40m.
Nunez 85m + 6m wages x5 =115m -40m mane fee =75m.
Extending sadio for 5 years at 320k, 16m X 5 = 80m.