No normal consumer is writing directly to S3, so the entire premise of your debate is kind of moot, that's why you're being downvoted. You're missing something

No normal consumer is writing directly to S3, so the entire premise of your debate is kind of moot, that's why you're being downvoted. You're missing something here, which is that DropBox are probably now spending roughly 10-20% of what they were paying Amazon on an annual basis. The savings probably grow as DropBox grows. Those savings over your hypothetical 5 years could probably keep DropBox on life support for another 5 years.