You are right...there is hanky panky going on in the building work. I don't know if it is widespread, and I do know they have independent auditors that review the expenses.
In our KH remodel, it came to light that the WTBS asked for bids for the general contracting work from outside, and one from the building committee. That is so the WTBS can decided what the loan will be to charge the congregation. It turned out the building committee bid was HIGHER than the other general contractors bid. So the the loan the congo pays back is at an higher amount with most labor done by volunteer.
It's a nice racquet. The elder and servants who discussed this with us were shocked. But I guess not shocked enough...life goes on as usual.