Wrong. Some might cost $100k, others cost much more.
"every counter missile Israel shoot to intercept the $100k missile costs $3.5 million"
Wrong. It depends which system is being used.
In the end, it's probably not going to matter as much going forward.
Now Israel has full air superiority it's tankers can fly near the border of Iran and allow their fighter jets to refuel without returning to station. Have you wondered why Iranian ballistic missile waves have slowed to a crawl?