Well, I decided to take a chance and order some of those $10 Chinese blade holders. I purchased two individual ones and one with some blades because that was the only way to get springs.
I'm not overly impressed with the quality so far. The finish is so-so, with the knurling on the adjustment knob being particularly rough. The threading of the knob or body is a bit off somehow, giving the adjustment a "gritty" feel and they're very stiff.
I think the real story, however, is in the body diameter. I measured the standard holder from Graphtec at 13.90mm. Of the three holders I bought, one is 13.92 and fits into the carrier fine. The second is 13.98 and fits, albeit tightly. The third holder is 14.08mm and doesn't go into the carrier at all, based on the second one I'm guessing 14mm is the absolute max size (the Graphtec carrier has three ridges inside, making it impossible to get a micrometer measurement).
I'm not an expert machinist but I believe a variation of 16 thousandths in three samples is pretty sloppy. Looks like they're being produced either by amateur machinists or using cheap lathes with lots of play in the mechanisms. Or amateur machinists using cheap lathes.
I'm trying to work out an exchange with the seller for the non-fitting holder, but that's been a frustrating experience. He keeps sending me links to YouTube videos on how to insert and adjust the blade/holder. After sending him the actual measurements and getting a little snippy in my last message I think he's finally agreed to just send a replacement.
So far, in actual use, these holders with the blades don't work very well. I don't want to muck around with my finely tuned standard holder, so I haven't tried one of these cheap blades in the Graphtec holder or the Graphtec blade in the cheap holder. I have some Clean Cut blades on the way, we'll see how that turns out. Hopefully I can manage to make these holders work with a little tuning. If the seller doesn't want the defective one back I may even try putting it into my lathe and turning it down to fit. Might even polish them to make them prettier