Walter got some more ultra cheap power supplies from AliExpress []. The price was still in the 'overly affordable' category, so here's another dissection.
The three bottom left connectors are for the AC circuit, the two bottom right ones adjacent to them are the DC circuit. This one looks almost sensible.
So let's get to the bottom of it:
The R2 resistor is sitting on the copper trace of the bottom leftmost connector of previous picture. So it looks like the 240 AC circuit traces are separated by healthy-looking distances. Likewise there is a good separation between the 240V AC and the 5V DC circuit.
We have tested this supply with a dummy load, when we pull 4.99 A the voltage drop is below 0.1 V, temperature of the supply did not rise overly much (the probes for measuring the current got significantly warmer at 5A). We think these power supplies are good to go.
(my legal counsel Flok told me that since I am not a electrical engineer I should provide caution and point out that people should use common sense etc., I hate armchair-lawyers)