>>58Cost is a non issue for industrial control systems. Businesses sink millions into their equipment; they do not give a shit if the PLC attached to their anus haxxinator adds a couple thousand dollars. They do, however, care very much if a cheap control unit malfunctions and damages equipment or injures the operator.
Control systems are built the way they are because they are subject to hard real time constraints, solutions to those constraints are well known, predate mass market consumer microprocessor systems, and have limited applicability to the latter.