pump monitoring methods and costs question

Anyone have any thoughts or suggestions on the best way to monitor typical building water booster pumps that are low cost and easily integrated in to the plc/control box? I see lots of high end, expensive sensors used on very expensive pumps in manufacturing process but for my purpose ie. domestic booster pumps for water supply to a building, the cost of these sensors would be more than the price to replace the pump. In the past I see where simple aquastats have been place near the pump to detect a rise in heat to signal shut down. What are some cheap reliable pump monitor sensors currently being used for these purposes?
 
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