Great finds. Been noticing this trend on Amazon and eBay. Is it that Ali-ex is getting expensive or Amazon cheaper? Nothing beats Amazon's convenience. Placed an order for cassette. I would have ordered the ospw too but there's no R6800 compatible one on sale.
Yeah, sometimes you really have to dig to find these items. There are probably thousands of small sellers on Amazon, sometimes items never appear on top searches, so it takes a bit of digging to find the good stuff. Also I used to run 105 5800, but I much prefer the shadow RDs based on ease of tuning, bigger cassette capacity and better protection from bumps and falls. If you ever come across a discount 105 or Ultegra R7000/8000 short cage, these OSPWs are basically mid-cage designs. I'm not sure if they help or not, but I don't think they hurt either!