Donald Trump's campaign made $80,000 per day selling their red hats, according to his son-in-law.

In an extract from "Breaking History," obtained by The New York Post, it was revealed that former President Trump designed his own red hats.

The Trump Organization initially only ordered 100 hats, despite Trump's request for 1000.

The hats soon became popular.

The hottest thing on the internet was when Trump wore the hat.

The demand for hats was so high that I worked with another person to create an online store.

Brad Parscale, who ran the Trump campaign's website, began spending $10,000 a day on Facebook ads to sell the hats, according to a letter written by the president's son-in-law.

He said they bypassed the budget restrictions of the campaign manager as they banked on the fact that they would have positive results by the time he noticed the large expense.

Most of the campaign's overhead costs were funded by the tenfold increase in online hat sales.

The New York Post cited previous analysis that said it costs between $2 and $3 to make a hat. They're usually sold for between $25 and $30 each.

The hats could have brought in $29 million in revenue if they brought in $80,000 a day.

The memoir about his time as a senior adviser to Trump will be published in August.