5B requests/day is ~60k/second, that's big but nothing insane. There are numerous frameworks/setups that can do far more than that on a single machine [1]
popular unmetered options: he.net, ovh, hetzner - You generally lose a lot of the "cloud" capability with these options however.
cloud options: digital ocean egress is $0.01/GB ($0.005/GB if you buy it via droplets), linode is $0.02/GB, vultr is $0.01/GB, etc.
[1] https://www.techempower.com/benchmarks/#section=data-r18&hw=...