You’re not factoring in worldwide distribution - not everyone lives in the USA, and costs worldwide bandwidth costs vary a lot.
Also we don’t know the number of http cache check requests. I’m assuming they number is way, way higher than the number of fonts served? That can cost you 160 million alone, with no bandwidth.
35kb sounds like the basic (mostly latin-1) subset. The size will vary a fair amount depending on which subset is selected, etc. In any case, fonts will almost always be served compressed, with WOFF2 being the vast majority of requests.
You are correct. I used the same match, except I used a 1mb gzipped Roboto font family package. I now realize that what google actually serves up is a subset of that.
* each font load is 170 KB (I downloaded Roboto and that's the file size of one weight)
* 36.3 trillion font loads (per the source)
* 36.3 trillion * 170 KB/font load = ~6171 PB [0]
Plug 6171 PB into the GCP calculator [0] with all egress via GCP Cloud CDN to N. America and the bill comes out to just shy of $130 million.
OP is off by an order of magnitude by my napkin math, but it's closer than I was expecting.
[0]: https://www.google.com/search?q=36.3+trillion+KB+*+170+in+PB...
[1]: https://cloud.google.com/products/calculator#id=f75c7bdd-4c4...