Not sure how long it will last but $21 a piece for an Aeon Labs DSC06106-ZWUS - Z-wave Smart Energy Switch is a pretty good price.
Fulfilled by Amazon so free shipping at $35 or if you have Prime. Just snagged 3 of them.
Comes up as regular price but at the bottom where you can pick from other dealers there are new ones from ZWaveProducts for $20.95+.01 shipping. Sadly the order does not add to give you free shipping on other items that are below the $35 amount.
Unfortunately they already sold out at the Amazon fulfilled seller by the time you tried to order. Not surprising at that price…
NP. While not fulfilled by Amazon, I still was in for 2 at @21 each. Great price.