I have a knockoff (or a 'copy', as some like to say) Yue Minjun piece from one of these places. Aside from a couple minor flaws, it's actually fairly high quality. Having it framed was about 13x more expensive than the painting itself.
The issue is that shipping prices are by weight, and the frames are usually much more heavy than a piece of canvas. This significantly drives up the total price of a frame from China, and lets American framing companies charge much higher prices.
Pro tip: get the artwork in a size that already fits a standard frame size and you'll save a ton of money.
Which is precisely why I brought the canvas home in a tube.
>Pro tip: get the artwork in a size that already fits a standard frame size and you'll save a ton of money.
Eh. I looked at such options, but wasn't impressed. Ended up settling on a fairly oddball, incandescently red glossy frame. Goes well alongside the subjects (a bunch of PLA guys).