The World Meeting of Families is declining to say what it spent on travel for the Pennsylvania delegation, which included Gov. Corbett and his wife as well as Nutter and his chief of staff, Everett Gillison.
The nonprofit also declined to disclose who has contributed to its fund, citing donors' expectation of privacy, except to say the archdiocese pledged $1 million, half of which has been donated.
The money being raised will go toward coordination of the eighth World Meeting of Families, an international, Vatican-sponsored, five-day event expected to draw hundreds of thousands of visitors.
"The World Meeting of Families understands all donors to have an expectation of privacy related to any gifts made," Meg Kane, spokeswoman for the nonprofit, said in an e-mail. "We would only make a donor's name/gift public upon the donor's request."
The nonprofit, which registered with the state in 2012 and is closely affiliated with the archdiocese, is not bound by the same IRS-related disclosure requirements as most nonprofits because of its religious nature.
The delegation to Rome, from March 23 through Friday, also included Archbishop Charles J. Chaput, the president and board members of the World Meeting of Families and their spouses, Kane, and support staff.
The nonprofit is led by Robert J. Ciaruffoli, chairman and chief executive of ParenteBeard L.L.C., an accounting firm. He went, too, as did several area business executives on the nonprofit's board.
The governor's security detail's airfare and hotel stay were paid for by the state police. Team PA Foundation, a nonprofit that encourages economic development, picked up the tab for Corbett's director of communication, Lynn Lawson.
Meals were paid by the World Meeting of Families, Kane said. Everyone stayed at the five-star Grand Hotel de la Minerve.
The mission to Rome was hailed as a success by those who went. But the group came back with only a polite nod and smile from Pope Francis, who canceled a private meeting with the group and instead gave it a few minutes as part of a larger, public event.
The visit prompted some questions Wednesday from City Council members at a budget hearing. Councilman David Oh asked the city's commerce director, Alan Greenberger, about the cost of Rome and the five other international trips the mayor has taken since 2011.
"My issue is, what is the purpose and what is the process?" Oh said after the hearing.
Unlike the Rome mission, Greenberger said, most international trips are trade missions, financed by Select Greater Philadelphia, an arm of the Greater Philadelphia Chamber of Commerce, and partially funded through the city, with a goal of recruiting business to the city.
Oh said he wanted to see the return on such investments. Greenberger promised to get him some figures. But before Nutter takes his next trip, Oh asked a favor.
"Please don't give out those [miniature] Liberty Bells," Oh said later. "That's just embarrassing."
The pope got one.
Correction: An earlier version of this story incorrectly reported the fundraising goal of the local non-profit.