There’s a bit of a war of economic attrition going on here. Are Israeli missiles cheaper than Iranian munitions? Can Iran replace munitions as fast as Israel is destroying them? Israel’s GDP (2017) was $350b vs Iran’s $440b. If every dollar of Israeli munitions is destroying $5 worth of Iranian weaponry, this could be a real drag on Iran’s appropriations budget, especially in view of the fact that Iran is also financing the Houthi rebels in Yemen, and firing expensive ballistic missiles at Saudi Arabia. For reference, Saddam’s Scuds cost $1m a pop.
“Are Israeli missiles cheaper than Iranian munitions?”
That’s a problem. The Israelis have excellent missile defense systems (Iron Dome, Arrow, etc.), but each battery costs 50 million (they have 10 - aiming for 15), and each missile costs $40,000.
Many of the Palestinian/Hamas missiles are made or assembled in the Gaza Strip and the West Bank, which would make them much cheaper than their Israeli counterparts. There are reports of Hezbollah in South Lebanon having tens of thousands of missiles (Katushya, etc). If so, they could rapidly deplete the Israeli missile defenses - one example of how “quantity has a quality all it’s own.”