I know that in the area where I live on the West Coast, most, if not all of the "vendors" for the RBC items are "brothers". Not directly WT owned companies, mind you.
For example: Chairs (if needed) are usually outsourced, but specifically upholstery work done by a JW owned company. Decorations, done by a JW firm. Woodwork (podium/lecturn, bulletin board), JW oufit. Bathroom fittings (toilets, urinals, sinks, dividers, water fountains, towel and soap dispensers, etc etc) provided by a JW business. Catering/food service, JW firm.
I worked for the RBC in accounting, and have seen the invoices from the JW firms for these products and supplies. Obviously installation labor is provided free of charge, but the JW Firms that provide the items still get paid handsomely to either provide them, or make them (like the podiums, info boards, cabinets, etc). The prices they are charging back to the RBC, and ultimately the congregation, are NOT bargain prices. Typically, they are equal to or greater than normal everyday pricing points. I was a little flabbergasted at what some of the "brothers" were charging for stupid stuff like "wall decor", and "bathroom cabinets". NONE OF THEM do it for cost. ALL OF THEM tack on a nice tidy percentage for profit.
There is no "bidding" process, or contracts issued, like a typical, normal commercial entity. It goes purely off the Good-Ole-Boy system. Its all in who you know.
Kind of like the used/turned in Circuit Oveers auto sales business that charges above KBB prices. Nice way to take advantage of one another.
Reminds me of government spending... Other People's Money.