Hello Fairmind,
When I was involved, they served food at the Circuit Assm cafeteria. This often cost about $1000 to purchase. Then they always have to spent 2 to 5 hundred on plants to decorate the stage.
As evil force mentioned there are CO and DO expenses. This is a two week expense because the DO spends a week with the CO (scrutiny time for the CO) before the assembly week. Then whatever extra expenses the CO has incurred since the last assembly must be covered, such as insurance, new tires, etc. Many circuits now provide apartments for CO's. Even if it is in a KH, that KH will usually receive compensation from the circuit since it is a circuit expense. This too is covered by the income from circuit assemblies.
And as pointed out, caretakers are not free. While paid Bethel wages they have all their personal expenses paid by the circuits that use the WT assembly hall. This is more or less presented as a bill to the circuits.
The grim fact is, it is far cheaper to use civic centers. They typically cost about $1500 for a week-end. They have events going even during the week days to cover their costs. JW assembly halls lay empty. Community Centers owned by local govts are more willing to operate at costs since their main purpose is to bring in bed tax money by sponsoring events. And they do not feel obliged to send $500 to $2000 each week to the Watchtower Society.
Perhaps the reasons for going to Assembly Hall operations instead of using local facilities is more obvious now.
Jst2laws
Ps, The Houston Tx Blain Wilson, City Overseer, swung a deal where the bros would cover the Astro Dome floor with ply-wood to be covered with dirt for the Tractor Pulls and Truck Shows. In exchange for the labor they got the Astro Dome several times a year for ONE Dollar. Now they have their own Assm Hall which cost tens of millions. I hear it is a real struggle now to pay for it.