Something worth keeping in mind is that Chinese factories that makes things like IP cameras don't typically have their own (significant) R&D departments and instead work from examples provided by the makers of the chipsets. Sometimes there will be another company involved that provide an "IoT ecosystem" (Tuya is a major player here: https://www.tuya.com/solution/hardware/ip-camera ).
So it's not necessarily surprising that the backend still works even if the manufacturer (Amazon brands are not typically the factory themselves, for practical reasons frequently changing "brand names" are used) is no longer present.
Since the topic of the article is about reverse engineering, I think it is extremely important to remember this. R&D time is very expensive. As people predominantly in CS, we should be aware of this, as this is typically how we are classified. And I think everyone innately knows how much more difficult it is to create something from scratch, the help you get just by having a reference, and how much easier it is to copy (or modify) when you have the thing in your hands (or source).
And it is worth noting that prices are vastly different in China. Labor is much cheaper and licenses aren't respected. The cost of living is cheaper to a smaller profit margin goes a much longer way. As tfa mentions, there are identical cameras sold by different manufacturers. It is unclear if this is typical reskinning or designs being taken. Both significantly reduce the cost of things. I have no idea how much hosting costs in China.
Regarding hosting, it's a big pain point for companies building these systems out of China as the "great firewall" makes it really hard to have reliable connectivity between the Chinese Internet (and datacenters) and outside. The ap-east-1 zone of AWS, based in Hong Kong, is very popular in that context as it tends to be accessible from both sides (so cost is fairly typical of AWS costs in that case). Alternatively Alibaba also have cloud datacenters in Hong Kong with similar properties.
