Allen-Bradley 1794-TB3S is a Flex I/O Terminal Base Module, not a full PLC controller, and prices vary significantly by seller and condition, with new units ranging from about $170-$180 on eBay and through industrial suppliers like Radwell International (around $178) or Quick Time Engineering (around $180), while used/refurbished options are cheaper but may lack factory warranty. You'll find the best price by comparing new vs. used from various industrial automation parts suppliers like MROPLC, PLC Hardware, and Radwell, looking for "used" or "refurbished" units from sites like SIGMA Surplus for lower costs.