To save you a click: no, the author does not provide any source for the headline.
Unfortunately, people are swallowing the headline without any critical thinking.
TFA kind of did, with the '20-30 dollars per person, per month, across an organisation' quote / comment - though they didn't do the math for you.
But that range of monthly spend only needs 220-400 ish people to reach the headline figure of $100k.
Whether that's good value, who can say.
The math on the 'if costs keep rising' bit of the story would take a hefty amount of (the bad type of) oversight to get to that figure per developer, yes.