The US uses APKWS and similar against Shahed-136. These guided missiles are cheaper than the Shahed-136. Why would you assume the US uses Patriot missiles against a Shahed-136? That isn’t part of their doctrine and the flight profile is a poor fit.

These have been operational in the US military for almost 15 years now and are widely deployed in the Middle East. You may want to update your priors. The US military anticipated all of this.

While these are cheaper than the Shahed-136, lasers have the advantage of unlimited magazine depth, so it is obvious why the US would invest in that.