have read this comment several times and I still cannot reconcile this point. How is the WBTS a publishing company when they don't "charge" for their literature? There are no advertisements in their publications. They mention the donation arrangement, but they will still leave you literature if you don't want to donate.
All aspects of publishing, (research, writing, printing) are done by the volunteers who live at Bethel. All apsects of distribution (inventory and offering to the public) are done by volunteers at the kh by literature servants and publishers. There is a guaranteed customer base (jws) who pay for the stuff and then collect donations door to door which are sent to the WTB&TS.