The Pilz company has a remarkable safety product philosophy. One of their R&D managers once told me, that each product development engineer is repeatedly reminded a mind game: "Imagine, you are the maintenance technician that has to crawl into the load opening of a huge hydraulic press like used in the automotive sector - would you really trust your electronic shutdown device, that prevents the press from operation during your maintenance job inside the press?"
Highly automated 24/7 production lines (automotive and so on), cannot be easily shut down for parts replacement or maintenance. So the maintenace crew has to work under conditions with running machines surrounding them, just protected by safety electronics but not really shut down and locked.
For special safety products, Pilz also has several hard&software teams in parallel on the same device design project. The teams have to use different software tools like compilers and they have to implement the required safety functions on different MCUs from different manufacturers. At the end, the resuts of these teams are put together into a final device, containing several signal paths from input to output in parallel, each path with its own firmware and MCU type, and some kind of majority voting over these signal channels is done.
Another speciality of Pilz are emergency stop switches that trigger high current contactors (relays). To make sure, a normally never used emergency contactor will not fail due to sticking mechanical parts after years of permanent "on-only" operation, the safety circuit from time to time turns off the contactor for a few milliseconds, just to detect the starting movement of the solenoid armature and then turns it on again - without "really" breaking the shutdown circuit.
There are decades of safety know-how behind such products for functional safety. And they have all the safety approvals, needed for technical applications that are hazardous or life threatening. That makes the price, even for low-tech components.
Tom