A better way to put it would be: how much would it have saved to not have to shoot them down to begin with?

Israel is desperate to keep wars going to justify their annexing of Gaza and West Bank and leech off the US.

How much would it cost NOT to shoot them down?

That's a legit point, though I think that there's also a very real point that we need more-cost-effective counters to shoot down low-end weapons.

We've focused on increasingly-high-end systems for a long time in the air defense world. If you're going to have everyone running around with explosive-bearing quadcopters and $20k craft that can precisely deliver a munitions payload 1,600 miles like the Shahed-136, we're going to need to have cost-effective counters.

Not to mention the scale-up question. Let's say China started mass-producing weaponized DJI drones tomorrow, which I expect that they probably could without too much trouble. Maybe we can hypothetically develop a cost-effective counter, but how long is it going to take us to get that up to scale? And what are the implications if we can't?

Supposing China has a cheap aerial delivery vehicle that releases weaponized quadcopters over Taiwan, lets them land and go to sleep, waking up only periodically at specific times for instructions. The vehicle is cheap enough to be attritable, and the quadcopters obviously are. Maybe you could even use subs to deliver them. Is there anything we can do to counter that, or does Taiwan just face an overwhelming deluge of precision-guided anti-personnel/anti-vehicle weapons that China can activate at any point?

We have good counters to a lot of high-end weapons. I'm not sure that we have good counters to massed low-end weapons. And I've read enough articles from folks commenting on the military situation concerned about it that I kind of suspect that I'm not just missing something obvious.

That's the point of iron dome system. It only shoots down rockets that would otherwise hit targets that would cost more to rebuild/restore. At least that's the case with hamas rockets - they are predictable enough. Drones are a different story.