This is true, but S3 does support replication (including deletion markers), and even 2-way replication, between two regions. Definitely not the same thing as a dual-region bucket, but it can satisfy many use cases where dual-region bucket would be used otherwise.
https://docs.aws.amazon.com/AmazonS3/latest/userguide/replic...
Also you can then create a single multi-region endpoint for those so I don't know why this person says it doesn't exist: https://docs.aws.amazon.com/AmazonS3/latest/userguide/MultiR...
You pay for durability and availability in the form of disk overhead, CPU, and network. Each encoding scheme has some expected cost. If your overhead for one-region is $X per gigabyte, then generally speaking, the overhead for two-region is going to be less than $2X—each region is more durable + available because of the copy stored in the other region.