US forces have been answering the wake up call for the last few years.

The main weapon that Apache's use to hunt drones are laser guided rockets (APKWS) with a per-shot cost around $30k (https://www.airandspaceforces.com/apkws-base-laser-guided-ro...)

These weapons have been fitted to most US tactical fighters for the counter drone role as well. APKWS is also not a "new" weapon system - it started fielding back to 2012, and was adapted into the counter drone role.

There are other lower cost (compared to legacy systems designed to take on manned aircraft) solutions currently deployed. The US Army has the Coyote, which is in the ~100k range.

Beyond cost of munitions, you have to consider that cheaper systems are going to have less range, and therefore you'll need more launchers, and you can start running up costs that way.