You still have to consider whether it's worth it to spend a patriot missile to intercept a drone, vs letting the drone hit, say, a billion dollar radar installation or a dozen troops.
On the manufacturing side, nobody said that all drones are intercepted with patriots. You have to look at the avg cost to intercept vs the average cost to attack, and if the ratio of those avg costs (across all attack/interceptions) is, say 100:1, and the combined GDP of the defending nations vs Iran is 1000:1, then what is the problem?
There are lower cost ways to intercept already on the market and being rolled out. See for example: https://www.defensenews.com/global/europe/2025/09/11/uk-to-p...
This whole "cost analysis of patriot vs drone" examines the worst case scenario at a fixed point in time and ignores layered defenses, the effect of combined GDP, learning, diminishing capabilities of attackers, and improvements by defenders.