As you probably read, this battery pack replacement using Chinese cells cost U.S. $11k in Hong Kong. These cells were described at Samsung SDI 120 Ah copies although they look quite different from Samsung's cells. They appear to be assembled in proprietary modules that aren't the modules that BMW used although it's a bit difficult to know for certain. The replacement battery pack is claimed to have a gross capacity of 48 kWh. Some have claimed that BMW's 120 Ah BMS doesn't support a usable capacity greater than 40 kWh, but it's not clear whether a proprietary BMS is included. I don't know whether the customer can keep the original battery modules and cells. It appears that the original battery pack compartment is being used.
A big red flag for me would be battery cell quality. I don't trust Chinese battery cells of unknown origin to be of the same high quality as Samsung's although they certainly could be. When I owned a first-generation Honda Insight hybrid, some third-party replacement battery packs used low-quality Chinese battery cells (or maybe more accurately, cells not designed for the high current requirements of the Insight's battery pack). These battery packs failed fairly quickly. A third-party battery pack supplier would need to be an established company that would be almost certain to honor its warranty, and I would want that warranty to be long if I paid more than $11k for the battery pack.
At some point, third-party i3 battery packs will almost certainly become available in North America if quality cells at reasonable prices become available.