My company has had an ongoing PLC related global maintenance survey since the year 2000. The majority of the participants back in 2001, reported 3-6 PLCs in their facility, that they know of. Granted most participants are managers and don't open electrical panels much, but many of the participants are from fortune 500 companies having hundreds of employees. The odds are most of them have 12-30 PLCs in their facilities. Currently the average is 6-9 reported, so the good news is the industry as a whole is becoming more PLC aware.
It is common to only learn about a PLC once the machine is down and the clock is ticking at a thousand dollars an hour, or more. Unfortunately, it is also common that after the fire is out, it's on to the next fire, without fully learning what can be done to avoid these costly downtimes in the future, and in other similar machines in a company or corporation.
Some older electrical panels may only have relays in them, but most machines are controlled by a PLC. A bottleneck machine in your facility may have a PLC. Most plant air compressors have a PLC. How much would it cost if the bottleneck or plant air shut down a line, a section of your facility, or even the entire plant?