why do you think they are a rip off
Because they are only half stainless, if you want fully stainless including the bolt then one has to pay more and their not cheap for what they are. I've seen W5's for £10 + 5 postage for one clamp

Plus their sizing is set in such a way that one could measure the circumference of the pipe, order a clamp only to find out after tightening that you need one size smaller or larger and then have to order a different size. Clever marketing in their design that. Or try and tighten them that little extra and risk snapping or threading the bolt

been there done that before.
OEM ones will only work with OEM parts not my cans. Best clamps I have ever had where the Micron ones which where supposedly stainless but they eventually rusted. I guess it comes down to the grade of stainless steel, there's different marine grades and they all have different properties, some are more corrosion resistant and some handle high temps better.
(:-})