DHS Collection of Conference Fees from Nonfederal Participants in DHS Conferences: FY 2017 (Fiscal Year 2017 Report to Congress) [open pdf - 437KB]
"In FY 2017, U.S. Customs and Border Protection sponsored three conferences for which nonfederal participants were charged to attend. The three conferences were conducted at a total cost of $474,348, and nonfederal participants were charged $276,973. A detailed breakdown of this event is provided in the data report below."
U.S. Department of Homeland Security: https://www.dhs.gov/