I always thought that was hyperbole. But in fact, the annual cost of a US aircraft carrier is not much different than annual US aid to Israel every year.
The US sends Israel about $3.8 billion in aid every year. How does that compare to a real aircraft carrier?
An aircraft carrier's operational costs, including the ships required to defend it, is between $6 million and $8 million a day. That's between $2.1 billion and $2.9 billion annually. If you add the amortized cost of building the aircraft carrier itself (the Gerald Ford cost $13 billion) over the expected life span of 50 years, and you can add another $250 million to those annual numbers, and the amount the US pays Israel is not far off from the cost of a single aircraft carrier group (of which there are typically nine in service at any time.)
But most of the costs of the aircraft carrier are sunk - the US doesn't get much back. From Israel, though, the US gets invaluable intelligence as well as a partner in weapons design and testing that saves hundreds of millions of dollars. The US benefits from the relationship with Israel in many other direct and indirect ways. It costs much less for the US to invest in Israeli rocket interception technology than to develop it from scratch, for example.