I cannot address Watch Tower finances during the Rutherford era. During Russell's administration they were shaky and by 1916 the Society was nearly broke. This was partly due to Russell's obsessive need to see his books circulated. He let colporteur accounts fall ten thousand dollars in arrears, only to be bailed out by a wealthy adherent. A court examination of Society accounts in 1911 showed that his books were a money losing proposition.
Russell may have been a fanatic, but he didn't make money from his writing. His goal was to spread Watch Tower doctrine at any cost.