It's probably based on the same new Realtek platform as the ones with 4 RJ45 + 2 SFP+. If the total switching capacity is 60 Gbps, that seems to be a good indicator. Those unmanaged models regularly sell for $50-80 on AliExpress and Amazon. The additional cost of adding management isn't necessarily all that high if the platform vendor (Realtek) provides a generic firmware base they can use.
This new platform probably isn't all that expensive, so that's probably the answer to gow they can sell them for that price. Not bothering with regularly certifications probably also help a bit. I also imagine that they lower their margins a bit when selling to the domestic Chinese market.
There even switches sold on AliExpress without English UI, so that's certainly a good thing to confirm beforehand when buying on Taobao.