He then told me that he was convinced that the Society has some gain and somehow supports the travelling of people from Bethel or other higher ranks with this money
True. Hotels and motels provide free rooms based on a number of guaranteed reservations. Once while working at a series of conventions some distance from my home, I was given one of these freebies for three nights so that I wouldn't have to add several hours of commuting to the 12-hour days required of [job description deleted]. It seems that whatever arrangements had been made for the use of that room fell through so rather than let it go unused, they offered it to me. I liked not driving back and forth, so next week when I arrived I inquired whether there were any unused free rooms. I was told they were all being used by VIPs.
Of course, to be fair, this is just common business practice on the part of the dubs. Conventioners have to stay someplace. This saves the WTS money. Other businesses and organizations do the same thing (although the rooms are usually a lot nicer).