The volley was fired at a massed coordinated strike of 6 Kinzhals, 9 Kalibr cruise missiles, and 3 Iskander ballistic missiles all arriving at the same time. All missiles were intercepted but one managed to incapacitate a single Patriot launcher after being intercepted (unclear if there was an actual detonation). A Patriot battery consists of multiple dispersed launchers, radar, and control units. It's hard to imagine better performance than this for an air defense system tasked with protecting a capital city.
The US has a variable capacity for Patriot missile manufacturing but its baseline far exceeds the 300 missiles per year that you quoted.