Actually the latter was effectively cheaper, because the winning bidder at auction typically pays an additional charge to the auction house, called a buyer's premium, that can range from 15% to 18%.
At a press conference following the auction, Brazilian Minister of Civil Aviation Wagner Bittencourt said that the high premium obtained from the concession verifies Brazil as a secure and opportune investment.
While the successful auction could be considered an economic positive for the entire area, the fact that the premium paid to secure these buyers jumped to 4.657% is a bit troublesome.