I know egress is one of the more expensive cloud services (e.g. compared to compute and storgage) at AWS, GCP, etc., but if I upload data to my learning system that's ingress AFAIK which is mostly free or less expensive. Btw. current Egress is like 0.1$/GB, so 100G ~ 10$.

Don't get me wrong, I am not saying you should always train in the cloud, but I do not think slower Upload or Ingress are the limiting factor.