Almost every cloud provider outside of Azure and GCP have an s3 compatible offering . S3 API is de-facto standard for object storage tooling

Cloudflare, scaleway, hetzner, OVH, Oracle, minio and dozens of others all have s3 compatible object stores

Most of them expect AWS have at least inter cloud transfer free (or discount Azure and GCP) being part of bandwidth alliance(BWA).

AWS S3 pricing is designed to keep you in the ecosystem , not be the cheapest, so tend to be costliest not cheapest unless your workload is archival.

For almost all non archival workloads egress costs will be on par or much higher than storage costs and AWS[1] charges a lot for any bandwidth.

AWS also makes migration really expensive so if you started with them, you are likely stuck as you would have to pay up to 10-12 months of cost to migrate out if you are on anything but the standard tier (cheaper the tiers higher the retrieval costs)

[1] All tier one providers have 10-20x b/w costs compared to tier two , however Azure and GCP discount for inter cloud transfers AWS does not

https://www.cloudflare.com/bandwidth-alliance/