sparky1 are you saying they didn't make a lot of money from the literature? From your figures they sold around 10 million Watchtowers per issue at 20c each. Double it to include Awake! (Slightly fewer Awakes! printed but I rounded the Watchtower figure down anyway) That's 20 million copies, 24 times a year. I make that just under 100 million dollars from magazine sales alone per year. Say production costs were as much as half of that, that's 50 million dollars profit from magazine sales alone.
Subscriptions didn't make a lot of money but they clearly weren't a loss. Because when the charge was dropped, subscriptions were dropped pretty quick too. Watchtower was not in the business of handing stuff out for nothing in return.
On top of that you had book sales, including quality hardcover reference books, Bibles, tapes, videos, calendars and everything else in the 1980s.
Plus my memory is that publishers would sometimes pay for the magazines themselves and give the money from householders to the world wide work in addition. I can also remember that householders would sometimes pay more than the cover price for the literature because it seemed so little.
Watchtower made its money not by charging large amounts, but through sheer scale.