I used to carry one of these windshield breakers in my ambulance days. They work great, one or two strikes and the windshield spider-webbed. I have a copy of them somewhere in my files, just don't know exactly where. It is a substantial piece of hardware, as Patty can attest. It does take a lathe and milling machine to produce.
Heat treating and chroming add additional cost.
It is certainly tough enough to deal with the canopy either as a lever or using the point. It also has many other uses such as digging a foxhole, disemboweling recalcitrant line guys or beheading front seat passengers. I found a guy selling knives and he had a plexi cutter that really shattered the stuff. The tip is very thick then ground to a sharp point. It only took a light hit to destroy a piece of plexi.