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CS2106 $ 7.50 $ 6.40 $ 5.10 $ 3.60 $ 3.32 $ 3.10 $ 2.80 Quote
Wasn't sure if that is the right one, but there's the price for that one.
Or maybe hack a Kill-A-Watt if they are only $29, can probably take the line to the LCD
There is also a Watt's Up device that has serial outputs for data logging. $139