The cash-for-honours inquiry cost Scotland Yard nearly £1.4m over 19 months, police have disclosed.
Mr Yates has defended the way the inquiry was run
The inquiry into whether money was donated to political parties in exchange for peerages, recently ended with no charges being brought.
Metropolitan Police chief Sir Ian Blair is to review the handling of the probe, amid concerns about cost and length.
Staff costs accounted for £1,304,549 of the total bill of £1,396,091, disclosed under the Freedom of Information Act.
The Metropolitan Police refused to provide a breakdown of the remaining £91,542.
The officer in charge, assistant commissioner John Yates had recently told MPs 75% of the "around £1m" cost were salaries.
He has defended the way the inquiry was run as "absolutely proper", saying the allegations were serious, and said it had taken longer than initially thought because he received "less than full co-operation" from some people involved in the investigation.
The investigation saw more than 130 people interviewed and four people were arrested.
Figures questioned by officers included the then Prime Minister Tony Blair and former Tory leader Michael Howard.
The inquiry was later widened from its original remit to look into any attempt to pervert the course of justice.
All involved in the investigation denied any wrongdoing and the Crown Prosecution Service said in July that there was "insufficient evidence to provide a realistic prospect of conviction against any individual for any offence".
Some Labour MPs have criticised the police decision to put so much time and effort into the inquiry, prompted by a complaint from an SNP MP, which they saw as a "political vendetta".
The Crown Prosecution Service disclosed last month that it had spent £122,000 on advice from independent counsel, before making the decision not to press charges.