The Trump administration isn't convinced the $10.7 billion set aside for space exploration in the proposed 2020 budget is enough to help put astronauts on the Moon by 2024. The President has submitted an amendment to the fiscal 2020 budget that would add another $1.6 billion. NASA Administrator Jim Bridenstine characterized the additional money as a "down payment" that would fund a lunar landing system, Orion, Space Launch System, "exploration technologies" and robotic explorers at the Moon's poles.
The amended budget will need to clear both sides of Congress before it can take effect. Whether or that happens isn't certain. This assumes no objections to the budget that lead to it dying in the House or the Senate, whether or not they pertain to spaceflight -- a wholly independent issue could sink the administration's lunar ambitions.
There are also unanswered questions about the funding. It's not certain if this is a one-time cost or will carry over to future years, and some in Congress might balk if this is a hint of increases to come. There's no question that a crewed trip to the Moon will be expensive, though -- so long as the 2024 goal is on the table in the first place, it may be difficult to keep costs down.