This is how they announce the biggest possible deficit:
The largest contributions come in at the end of the day. Now that assemblies are 1 day only it is common to only have counted the morning contributions to include in the report that is read from the platform. Those will always be pitiful. Depending on the circuit they often find it prudent not to include the lunchtime contributions which would make a big difference. Since these are counted after lunch and the report has to go to the overseer before the mid-aft announcements it's easy to excuse operating in this way. But when the announcement is made that “at this stage in this convention we have a deficit of $$$” that's why it's often a high percentage of the total “expenses”.
Now in terms of the actual expenses, yes for sure they are loaded as much as possible. But here is the way they are made up and why, even though the building is paid for, it's not just $100 to open the doors and turn on the lights:
To begin with it would be an error to think of the expenses in terms of one day of use. Things have to be maintained year round even when not in use, and periodically there will be reno's (yes, I know the labor will be free but there are still expenses). So think instead of the cost for a weekend being the expense of running the whole hall and keeping updated, replacing appliances, etc, for 10 years and then calculate as:
(Total for 10 years) divided by (10 x number of assemblies per year)
... in order to get a real cost. Okay remember I acknowledged that it is loaded, but it's not peanuts either.
One of the biggest additional items is the amount that they resolve to send into “mother” at the start of the assembly. This cannot be a conditional amount, so they make a guess in advance as to how much they can send without experiencing a deficit at the end and add that to the bill. Once committed this cannot be undone, even if it causes a deficit at the end.
On top of that will be added things like circuit contribution to a circuit apartment if there is one, CO and visiting speaker expenses, and any other ancillary costs that they resolve at that convention.
I don't know the basis for the new huge hike. The explanation publicly given was BS to be sure. The costs were already spread evenly. If there was a truly plausible and palatable explanation then I'm quite sure it would have been given, but I don't think even the regular elders understand it beyond this vague idea of restructuring.
I have heard that with this change several assemblies ran into deficits after the final tally this past year. Congregations had to top up the account afterwards. It used to be very rare for this to happen, but it seems to be becoming more common. Personally I think mother got too greedy and this will be an ongoing problem. But on the other hand if they can keep pushing and persuade the die-hards at all levels of wealth to increase the contributions as they are obviously trying to do, maybe they'll be able to pull it off.