There are, literally, dozens of hosting providers that bake unlimited egress into their offerings - still. Bandwidth is cheap and has only gotten cheaper. Remember that Amazon doesn't always need to pay for Internet access. It's very likely they participate in Internet exchanges tied to other large providers. Given Amazon has a massive footprint they likely participate in these all over the globe to reduce congestion on their Internet connectivity.

They very much have massive margin on egress. Given some of the cost comparisons floated today comparing R2 to S3 egress AWS is likely hitting 1000s of times (likely more) their return on the actual bandwidth cost they pay for month over month.