I am told, although I have no personal knowledge of this, that the GB members tend to be rather frugal in their habits and in their staying at hotel accomodation. The WBTS foots the bill. But they do have access to a credit amount that is not disclosed, and which can be quite generous.
This has not always been so, however. The last of the flamboyant leaders of the WBTS was Nathan Knorr, and he always travelled first class, and insisted that the society book two seats! Evidently he hated travelling with anyone beside him, so he kept the set next to him while he sat by the window.
He was also quite the man about town and a blatant sybarite. He enjoyed Saturday nights at the Broadway theatres, where he had special seats set aside for himself and any guests he had. He also evidently had a yacht donated by a Watchtower Follower, where he entertained suppliers for Watchtower material. All entertainment paid for by the Society.