'Why the lack of high precision cheap ohm meters?'
I wouldn't call a 1% milliOhm DMM delivered to your door for 140$ expensive, but hey, I know some people struggle in life, even in Germany.
The OP has no idea how to turn his 60$ CAT I DMM into a super duper micro Ohmmeter with 7$ of parts and if he ever manages it, I'll eat my hat.
That mA only CEM meter has the GS TUV markings on the faceplate and if you don't believe it is legal, do me a favor since you live in Germany and report the manufacturer for counterfeiting.