Azure is part of Cloudflare's Bandwidth Alliance[1]. If you use Azure's serverless functions and put your service behind Cloudflare, you'll get free egress.
I was aware of the bandwidth alliance, though looking on their KB for now it's only discounted egress [1]. Same with Google, though not part of the bandwidth alliance, data delivered through their CDN Interconnect program starts at $0.04/gb (NA) [2]
[1] https://support.cloudflare.com/hc/en-us/articles/36001614391...
[2] https://cloud.google.com/interconnect/docs/how-to/cdn-interc...