The eight Benghazi inquiries instigated by the Republican party were never about finding the truth which was already known. These were political campaign events and therefor the Government should be reimbursed for these expenses on the behalf of the Republican party. The cost estimate is based on an estimate by the IRS extrapolated for the 7th and 8th "investigations":
http://www.irs.gov/uac/Newsroom/Prepared-Remarks-of-Commissioner-of-Inte...