Thank you for the explanation regarding food.
WT create a per person rate which is multiplied by the number of publishers assigned.. Any lower amount of donations than forecast will be considered a deficit even when more than the true expenses have been collected. While the per publisher rate will include utilities and consumables, those will be small compared to the 'donation' to be sent to WT, making up the majority of the 'entrance' fee.
Consider that the account report is typically made early in the day. As someone here said, even if the majority of the expected donations have been received, much of those donations may not be reported when the accounts report is made, expecting attendees to dig deeper.