http://geekhack.org/index.php?topic=34996.0According to feng the second batch of MKC keycaps improved a lot. I think that case has a top quality as well. I will definitely ask my friend as he already got one.
Personally I think the Koala case is nicer and more solid overall, as the Chinese one looks a bit hollow.
Regarding the profit margin, you are probably right. However please note that Chinese manufacturing is usually way cheaper than to produce something in South Korea.
Also the machine shop used in the Korean manufacturing likely made profit on those cases, while there is a remote possibility that MKC is a machine shop.
Also the 325 USD price of the MKC is actually cheaper, though it doesn't include a custom plate. On the bright side, it is compatible with the Phantom and Filco, and you can chose a wide range of colors for the case.
The Koala came in either silver or black.
Regarding your comment about the Copycat design. There is nothing revolutionary about curved sides. Actually Steelseries implemented a similar design on they line of mechanical keyboards.
You can't stick those type of rubbet feets on the MKC, as it uses a different design to accomodate the non slip feets.