I was Literature Servant when the "no charge/donation/contribution" system was brought in. As pointed out at the time the literature maybe be without "charge" but not without "cost". In other words it still cost money to be printed and distribute it.
Of course what happened was that brothers/sisters began ordering things like Deluxe Bibles, Bound volumes etc, what were known then as "controlled stock" items. Before the change in the system a Deluxe Bible cost £6. After the change I would be surprised if anyone "donated" that much in the box at the Kingdom Hall.
Eventually I think this must have filtered through to Bethel. That brothers/sisters weren't as "honest" as they thought. I think most congregations in the area were having the same problem. In my congregation I think for every £100 of literature from Bethel we were only getting £50 -£75 in "contributions" if that. Eventually we received a letter from Bethel, I think all congregations did, saying that certain items would again be "controlled". We also received a "cost list" of "suggested prices for items".
I think the magazine side of things suffered more from the "no charge" system. Because many publishers didn't put any money in the KH box until they had actually placed them.