Yea, I removed the example scenario because it's kind of pointless, in order to zero in on bias.

I don't see how there couldn't be sampling bias. Salary is a sensitive topic, and people who are making on the high range (within FAANG or outside of it) are going to be more likely to want to post about it and answer surveys about it than people in the low range. HN and Blind are obviously not random sampling. levels.fyi claims to use self-reported offer letters AND reach out directly to compensation folks at companies, which is better. But are these individual companies sharing unbiased data?

When one encounters average numbers that are a little higher than their reality, it's disappointing but believable. When one encounters average numbers that just look just crazy, one begins to ask "am I really this much of an outlier or should I suspect methodology/bias?"