Dembele only signed for the La Liga giants last summer.
According to German outlet, Spiegel, he will cost €105m up front, with the possibility of €40m in add-ons.
Among those add-ons, is an obligation for the Spanish club to pay €5m, when the France winger reaches each of 25, 50, 75 and 100 matches played.
The report also claims that the 20-year-old penned a deal worth five times what he was earning with the Bundesliga outfit, a whopping €12million per year, up from the €2.4m he earned per season with BVB.
Dembele is currently out with a hamstring problem and is expected to be out until January, making it difficult for him to reach any of those match numbers before the end of the season