Subject: Re: Trump PAC paid Melania $155,000
The Secret Service incurred costs of approximately $396,000, primarily for Secret Service agents' temporary duty costs, while protecting Donald Trump, Jr., Eric Trump, and their spouses during three international trips taken during January and February 2017...

Per your link..
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'Asked why the president's three adult children who aren't in the administration were on the state visit, and who paid for their travel and related expenses, a White House official didn't address why they were there. "They are personally paying," the White House official responded.

Taxpayers still incur any Secret Service expenses for protecting the president's adult children, but those costs can be incurred whether they are with the president or not.'

https://www.cbsnews.com/news/w......