Not saying anything disparaging about Agency Power, B&M or any of the other proper manufacturers of quality parts. In most cases, it is a "You get what you pay for" world, and I am sure that these manufacturers take good care of their customers, and employing US workers is a good thing.
I am frugal as all hell, though, being programmed by demented post-Depression parents. I can't resist trying to get the best deal on everything. It's a sickness, and I am embarrassed.
That said, having just installed one of the $50 Ebay SSK kits, it looks functionally identical. CNC milled 6000 aluminum casing and bearing journals, steel lever mechanism, solid adjustable fulcrum bolt. I got a totally workable, better than OEM SSK for $50. Zero slop. Zero vendor support, either, but none was needed. Just another option. That extra $250 pays for the inevitable headliner replacement we face. YMMV.