Is this a realistic salary for China postdocs/ assistant professor? After reading this (Persistent issues with salary pay as a postdoc in China: What can I do?) I am kind of worried about working in China with regards to pay.

On paper, the type of salary advertised by some universities is fantastic for Chinese standards, even Western standards. 

For instance, on https://www.mathjobs.org, postdoc/assistant professor salaries are in the range of 200k-500k RMB per year. For Chinese standard of living, this is considered very good.

Is this a realistic salary? Any experience to share? I am a foreigner and do not know much about Chinese academia.

Also, this salary does not tally with what I read elsewhere online and speaking with some Chinese friends. According to them, 100k RMB per year is more of the norm in China for postdocs and junior faculty. The Chinese universities do give some other benefits like housing/research funding though.

Thanks.
Please take my answer considering my declared conflict of interests:
I am the author of the linked question "Persistent issues with salary pay as a postdoc in China: What can I do?". Here we are within just 5 days from departure and still the payment issue is a monumental struggle. 
I shall update my situation in that question soon after I am gone.

Now, directly answering your question. I have been offered another postdoctoral fellowship at CAS/Beijing for (theoretical) 250k/year. My friends in that same lab (lower salary, Chinese PhDs) claim they never had issues with being paid, stating they get 9k every month sharp. 
I have done some research around and in fact standard salary is within 120-180K per year, with the problem that typically some 35k off the total are withheld until the very end. They claim this is to ensure you'll complete your "duties". 
However postdoctoral salary offers are on stead increase, and now there are several places offering >200k per year, up to 280k per year as the highest I've heard. 
Mind you that the Chinese system works on a local logic of "meritocracy" which is solidly based on rankings. This means that highest salaries are offered to the youngest PhDs coming from top-rank universities from 1st world countries who published in top IF journals. These individuals will get offered >250k per year as postdocs with a wide margin for negotiating extra benefits.
This brings me to another point: in Chinese culture negotiation is never-ending. This means a signed contract is just a formality symbolising your engagement, and from that moment on rules and terms can and will be moved around depending on a complex game of mutual understanding. This is called "guanxi" in business in China and can be very hard for foreigners to understand &amp; digest.
Finally, this brings up again the issue I face while here. What was written in the original offer and even on contract may be quite different from reality. Carefully read the discussion at zhihu.com/question/52131526/answer/232792998. This is a top university in China offering attractive contracts for postdocs and locals are complaining they finally get a fraction of the promised figure. I know how it feels.

Realistically, expect earning anywhere between 8-12k a month depending on your "qualifications" for local standards, while working 10h per day 6x a week and being asked for more. Expect some dirty game around your payment, possibly involving potentially illegal activity (e.g. being asked to generate fake invoices).

All points taken, it boils down to your personal reasons for taking a postdoc, and why are you considering this and that lab, and why in China. If you're the kind of righteous law-abiding animal-loving individual who enjoys straightforwardness and openness, a healthy work-life balance, and drinking some wine with a good cheese on occasion... probably coming to China might not be a good idea. If you're seeking a stable salary pay and a professional work environment towards erecting as a established professional, probably taking a postdoc may not be the shortest nor surest path. 
I don't think you should focus your worries on salary, all the more in China where it may vary without warning.