Halloween is an important event for the United Nations Children's Fund, or UNICEF, as hundreds of thousands of trick-or-treaters go house-to-house asking for pennies or dollars to help the world's needy children. But according to the U.N. Board of Auditors, which monitors the organization's finances, the cost of funneling such private sector money through UNICEF's national committees to the global organization is getting so expensive that it merits special notice.

A report by the auditors that was published last June, but won't be considered by UNICEF's supervisory executive board until next year, highlights the fact that those national committees last year kept an average of 29 percent of overall private sector contributions for themselves, either as expenses or as stockpiled cash.

In all, more than $341 million in donations was held back by administrators in 2012, and more than $2.39 billion over the period from 2006 to 2012, amounts that the auditors dryly labeled as "high."

In fact, for six of ten unnamed biggest donors the hold-back rate was higher than 30 percent, the report noted, and in one case, it reached a towering 61 percent.