A few reasons: Because a Raspberry Pi and Ebay touchscreen won't be running or supported in 20 years, while the PLC will. The IO on a Pi needs optoisolators and

A few reasons: Because a Raspberry Pi and Ebay touchscreen won't be running or supported in 20 years, while the PLC will. The IO on a Pi needs optoisolators and hardening that's built into the PLC, and it needs soldering, while the touchscreen has built-in screw terminals. And while the software sucks, anyone remotely competent can go from zero knowledge to bumble into a working, sturdy product on the PLC in perhaps 80 hours. Qt has a much steeper learning curve. Essentially, the touchscreen is an RPi and touchscreen, plus some industrial enclosure, strengthening, and connectors all wrapped up into a product. That integration is definitely worth $400. Or, if you want the name brand stuff, the Allen Bradley version of the same will set you back another $2000.