Soft Starters Some Tech Specs To Read (nerd link)

That gizmo doesn't look like a complete soft-start module, just the main component to reshape the AC waveform. Missing the control logic, the voltage and current measurement circuits and the microprocessor brain to name a few.

I'm guessing a large part of the cost for RV soft-starters is the manufacturers of such things feel their microprocessor programming is printed on gold leaf. More than likely only $20 worth of components inside one, if that.

Cheap enough but the quality is questionable.

I was always under the impression that a 'soft starter was baby food.