I don't know the answers to the OP's specific examples, but let me make some general points:
This is the #1 factor. In the 1st world, everybody is trying to climb the ladder to having a big 4x4 parked outside (1 for the man, 1 for the woman, and the 2nd one needs to be a T80 tank for the school run which is extremely hazardous to the kids). Houses cost a fortune and most people and not paid off for 30 years. Mountain bikes cost 4k (2k before covid). And so on. Life is expensive and "life ambitions" are extremely high.
In China most factory workers do not (yet) have these expectations, so the ecosystem there caters for people who get a few hundred $ a year. Everything is pretty cheap. I know this as I come from a formerly communist country. You spent 5 years saving up for a TV (1960s). Rents were cheap, say $5/month. But you earned $20/month

A lot of stuff they use are made in the West but the mfgs sell into China for
far less than they sell down the road. For example Intel might sell a CPU in the West for $100 but they sell the same chip to china for $20.
Good economies of scale and proximity. You make something. PCBs are made next door. Metal boxes made 2 doors down. Injection moulding 3 doors down.
Compliance is mostly fake. CE declarations are fake. ROHS is fake.
China has a lot of capital equipment which was set up there by western firms, years ago.
A lot of stuff they are selling is stolen from the stock of a firm which went bust. Chinese mfgs go bust at a fantastic rate. The stock then disappears rapidly and pops up somewhere else. Nobody can keep track of it. The place is dysfunctional, tax evasion is rife...
There are govt subsidies e.g. DJI is heavily supported by chinese govt.
A lot of stuff is surplus stock which somebody just wanted to get rid of.
Western chip makers charge a lot because they can. So an STM arm32 chip might be $5 while the chinese equivalent (one of their "fake" 32f407 etc) is $2.
Add up all these factors and you get a much lower price.
However a $0.90 mp3 player was definitely stolen stock
