Robert Mueller’s investigation into whether the Trump campaign conspired with the Kremlin to try to sway the 2016 presidential election has cost taxpayers $3.2m over its first four months.

That is roughly the same estimated cost as a single presidential golfing trip to Mar-a-Lago.

The office of the special counsel released on Tuesday its details of expenditures from May to the end of September. The biggest amount for the team of lawyers and investigators who are looking into the presidential campaign is personnel costs: $1.7m.

The cost of the investigation is significantly higher – a total of $6.7m in that same period – when other expenses that are related to the investigation that were paid for by the DoJ directly were taken into account.

The office said those expenses would have been paid as part of the federal investigation into the possible Russia conspiracy regardless of whether or not the special counsel was involved. The special counsel office was set up in the wake of the firing of James Comey, the FBI director, by the White House.

Comey’s dismissal is believed to be one of the subjects Mueller is investigating.

The office is paid for by an “indefinite appropriation” at the Department of Justice, which is dedicated to funding special counsels.

The other high cost was travel: $223,643 for special counsel staff to travel and, in some cases, relocate in order to do their jobs.

The report revealed that the office has contracted out several important functions, including IT services ($111,245), transcripts ($24,456), and building costs ($17,217).

Four individuals have so far been charged in the investigation. Two people connected to the Trump campaign – former national security adviser Michael Flynn and former campaign aide George Papadopoulos – have pleaded guilty to perjury and are cooperating.

Two others – Paul Manafort and Rick Gates – have been indicted and pleaded not guilty on money laundering and other charges.

That’s about $800,000 per indictment.

It is not clear how much the White House has spent on the president’s frequent weekend getaways, but estimates range from about $1m to $3m per weekend.