To be fair, the WTS charges about 3% a year simple interest on a loan, which is currently about the rate of inflation. If interest is not charged, at least at the rate of inflation, it erodes the value of the fund. The local Kingdom Halls are not owned by the WTS, they are owned by a local not for profit which is the cong. holding the territory where the building is located. 3 elders are trustees of the property and the elders are appointed by the WTS, and yes, they will do whatever the WTS wants.
Of course, local congos. can rent or lease a facility instead of purchasing one. Either way, the expense is borne by the contributors who own nothing in the end, not even the "treasures in heaven" they believe they are accumulating for themselves.
The Assembly Halls, on the other hand, are a different story.