The Republican National Committee paid more than $300,000 in October to a company owned by Donald Trump Jr. to purchase copies of his new, self-published book.

Autographed copies of the book, Liberal Privilege, were given out to donors who contributed between $50 and $100 to the RNC, according to a source familiar with the arrangement. The source said the promotion raised substantial sums for Republicans in the final stretch of the election.

The RNC’s payment—for $303,892.47 on October 28—went not to Trump Jr. directly but to a company called Pursuit Venture LLC. Corporate records in Delaware, where the company was formed in late 2018 and lists the president’s eldest son as its principal. The RNC’s payment was itemized as “donor mementos.”

It’s common for political groups to buy books written by prominent public officials and offer them as gifts for their financial supporters, and GOP committees have purchased books for their donor promotions this year that were authored by people who are not related to the president, including Sen. Ted Cruz (R-TX) and Fox News host Sean Hannity.

But the RNC’s payment to Trump Jr.’s company in October was the largest single payment—out of more than 700—that the committee has ever reported for donor “mementos” or “gifts,” according to Federal Election Commission filings.

It was also more than three times what the RNC reportedly paid to acquire copies of Trump Jr.’s previous book, Triggered. The committee said, at the time, that its fundraising promotions using that book brought in more than half a million dollars, netting a substantial fundraising benefit for national Republicans.

There is a benefit for the author as well. The bulk purchasing of books by a political committee like the RNC means that aggregate sales for the book become artificially inflated. That, in turn, can help a book’s reputation by elevating it on bestseller lists.

Trump Jr.’s first book was, indeed, a New York Times number-one bestseller, and his sophomore effort topped the charts on Amazon shortly after publication—and before the RNC’s bulk purchase. Unlike his first book, which was published by Hachette, Trump Jr. decided to self-publish Liberal Privilege—as a “shot across the bow” of the publishing industry, he told Axios. Self-publishing generally means an author doesn’t get an advance on the book, but they do pocket a far higher percentage of the sales.

FEC records show that the RNC wasn’t the only one shelling out for Trump Jr.’s most recent book. Pursuit Venture also got an $11,000 payment in early October from Rep. Matt Gaetz’s (R-FL) reelection campaign. The purpose of the payment was listed as “supporter gifts.”