In an absolute sense, yes the federal government pays for itself. However, said dollars still get tallied, divided up into the relevant sub-budgets, and the bureaucracy of additional allocations have to be gone through in order to add in more funds. So if this story is correct, it means Trump is trying to avoid the usual budget allocation/funding process, either as a hope he can speed run a “victory” over Iran, is trying to avoid congressional scrutiny into this war, or a combination of both.