The latter figure represented an astonishing 86 per cent season rise compared to the previous year - another record high for the club.
"In the end, my conclusion is that; I do not want to be too positive but I think that Borussia Dortmund are well positioned for the future," Watzke told reporters.
"But we know as well that we are now in a crucial phase in terms of our sustainability in the sport.
"That is the only reason we have not sold Robert Lewandowski. All of us at the club - [general manager] Michael Zorc, Jurgen Klopp, me, the management and all other bodies - were all in agreement, because we want to bring the best possible team to the pitch this year.
"Therefore we had to make compromises."
Lewandowski, who reportedly has received a €3.5 million pay rise last week, was frustrated throughout the close-season as the club, he claimed, reneged on a deal which would see him move to Bundesliga rivals Bayern Munich.
However, the 25-year-old, who is in the final year of his contract, has drawn a line underneath the dispute and says he is ready to play for Dortmund.