Another aspect of this is that a lot of the weapons are taken from stockpiles
>>>The majority of weapons and munitions the U.S. government has sent to Ukraine are pulled from America’s own stockpiles using presidential drawdowns, since this program allows for the quickest delivery. The supplementals then provide the Pentagon with funding to replenish those stockpiles, which it does primarily through the military contractors that build weapons for the U.S. military. . . .
The vast majority of U.S. Ukraine-related funding does not go directly to Ukraine; it stays in the U.S. economy, subsidizing the production of weapons in
at least 31 states and 71 cities.
While Ukraine gets most of the aid in the form of old American weapons pulled from U.S. reserves, it’s American workers at American companies that make new weapons to replenish them.
America’s military-industrial complex also restocks inventories of its NATO allies who similarly help Ukraine.<<<
https://www.lawfaremedia.org/article/how-america-s-aid-to-ukraine-actually-works
If the weapons being taken from the stockpiles needed to be replaced shortly anyway, the increased cost due to early replacement might be modest. Having said that, I don't think I've seen a detailed breakdown on this.