ABMs are very slow to build, expensive, and doubtfully effective red herrings. PAC-3 manufacturing: regardless of having perfect, prioritized intellectual property sharing arrangements, it would still involve competing with limited quantities from monopoly critical suppliers and delay from deep levels of supply chain parts and assemblies vendors.

It would be better to catch SSM launchers on roads, rails, and inland waterways and dismantle the supply chain that produces/imports them and their parts with long range kinetic sanctions. (Kill the archer and arrow maker, not the arrows.)

Incidentally, someone in Russia may have believed they had a surplus of S-400's because it was using them as SSMs in nightly strikes on civilians rather than as SAMs and ABMs even though its last reported manufacturing capacity was only 40 units/month.

SAM - Surface-to-Air Missile

SSM - Surface-to-Surface Missile

ABM - Anti-Ballistic Missile (Anti-SSM)

But it's also exposing the effectiveness of asymmetric warfare. A single patriot missile, a single one, costs around $ 4 million, and its the only weapon that may intercept missiles that cost 1.5 up to 40 times less.

Even when taking the major Russian ballistic missiles like the Kh101, the Iskander and Kalibr the economics are better for the Russians between 4 and 1.5 ratio.

Moreover NATO has no weapon that can intercept the Iskanders which have had so far a 90% effectiveness. Good thing that Russia cannot mass produce them.

But here's the most interesting part: what you launch to intercept is not based on the cost of what's attacking you, but on the potential damage of not intercepting it.

If a 50k Shahed drone is on course to hit your command center or expensive aircraft you may still have to launch a Patriot to intercept it, you can't risk your high command being eliminated because the attacking weapon was cheap.