At least 10 staffers in Donald Trump Donald John TrumpBubba Wallace to be driver of Michael Jordan, Denny Hamlin NASCAR team Graham: GOP will confirm Trump's Supreme Court nominee before the election Southwest Airlines, unions call for six-month extension of government aid MORE’s campaign have been working for free, according to a Reuters review of campaign finance filings.

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Among those who haven’t been paid are former campaign chairman Paul Manafort, California director Tim Clark and communications director Michael Caputo. The campaign had also not been paying two aides who left in June to work for a Trump super-PAC.

Aides in such senior-level positions in presidential campaigns sometimes earn six-figure paychecks. For example, Hillary Clinton Hillary Diane Rodham ClintonJoe Biden looks to expand election battleground into Trump country Biden leads Trump by 12 points among Catholic voters: poll The Hill's Campaign Report: Biden goes on offense MORE’s campaign manager, Robby Mook, earned about $10,000 in July alone.

Kellyanne Conway, a pollster in Trump’s campaign who was recently promoted to campaign manager, wasn’t paid anything the entire month of July.

The campaign has spent just $89.5 million, while Clinton’s campaign has shelled out $268.4 million. Trump often points to his campaign’s frugality as a sign of his efficiency.