I think one point about 100k being a large sum is that we've been talking about "six figures" since the early 2000s, and adjusted for inflation we'd be talking about roughly 180k, i.e. approaching a factor of 2.

And the second argument about 100k not being a lot of money is mentioned by the author: there are many places (in the US and outside) where 100k will not cover rent and essentials. So yeah, in this way, 100k is not a lot of money, because it will not grant you any form of comfortable life in (Austin, Seattle, most of CA, etc.), which is where a large chunk of tech jobs are located.