This year they gave Israel $18 billion, so much more than usual.
In one sense, all of this is actually a jobs program for the US defense industry, since all that money is required to turn around as weapons purchases from US companies.
Even $18 billion is less than 1% of the US non-military budget, this isn't the reason we "can't afford" the USFS, or the reason to stop giving weapons to Israel -- the US certainly can afford both. (The reason to stop supplying Israel is that those weapons are actually destabilizing the region and encouraging violence and gross human rights violations).
But, no, Israel "buys" US weapons with US money, they are indeed a gift.
https://watson.brown.edu/costsofwar/papers/2024/USspendingIs...