The event -- which Trump called a rally earlier Saturday -- was held at the Norwood, Massachusetts, home of Ernie Boch Jr., a local car magnate.
"Most of the people came in free," Trump said Saturday at a gathering of the National Federation of Republican Assemblies, a tea party-aligned group. "I got so angry at my people because somebody put up a sign saying $100. And honestly -- first of all, it's peanuts, it doesn't mean anything -- but (the media) used it to try and marginalize. They always do. ... The bottom line is, I am self-funding my campaign. I'm self-funding. I don't need money."
The comments echo Trump's response Friday night when asked about the event.
"This is not a fundraiser," Trump told reporters. "I turn down a lot of money."
But the sign in question outside the event directed donors on how to contribute.
"Please have checks made payable to: Donald J. Trump for President, Inc. or cash ready on entry. Thank you," read the sign, which was later taken down after Trump's campaign manager, Corey Lewandowski, saw a CNN report.
Although the sign was taken down, several smaller signs depicting the same message remained at the check-in booth.
Hope Hicks, a Trump campaign spokesperson, said the campaign paid for the event, which is why they took the money. But Boch told CNN Friday that he was paying for the event.
"I am paying for the event tonight," Boch told CNN Friday. "I have invited my friends and acquaintances, and it started as a fundraiser but it kind of morphed into something bigger."
Later Friday, Boch told CNN's Don Lemon that the money goes to the campaign.
"Oh sure, (the money) goes to the campaign, sure, the checks are made out to Donald Trump," Boch said. "I don't know that it would cover the cost of the event, but we haven't really discussed it."
Asked later Friday to clarify, Hicks said the campaign was reimbursing Boch and that's why they were taking money. Hicks followed up in an email, saying the campaign was paying for the event and "any small contributions will go directly to covering the cost of the event."
Saturday morning, Trump tweeted that the event was a rally.
"Great rally last night in Massachusetts. 2000 people at a house - must be a record! Unbelievable spirit to MAKE AMERICA GREAT AGAIN."
Trump has disavowed raising money for his campaign, saying it is a corrupting influence on politics. He nevertheless has several super PACs and a political nonprofit group, which can accept unlimited contributions from donors, supporting his campaign.