Voltage Controlled Switches

I have bought a few of these and one is working now as my diversion load controller. The battery bank has appreciated the function often, even without my wind generator functioning all that well. I have bought another that I plan on using for a load controller. At NAWS they are $125.00, they were $85.00, that price I found to be pretty prevalent, to my surprise. Why are these simple things so costly? They are kin to voltage regulators I think, I can not find bargains on them either.
Always troubleshoot with adequate sunlight.  Hi Ho Hi Ho
2.3kW [10] Enecsys SMI-240-60 micro inverters