Offering redundancy across zones is one thing (and I'm pleased to offer it to my customers). Getting them to use it is quite another thing.
Even if it was "only" 2x or 3x the expense to have a completely multizone setup, the ongoing operational burden is too high to justify over the 2, 10, or 100 year timeframe when no outages happen which could have been avoided.
Companies dependent on a single Amazon zone just give up and wait during a zone outage, blame it on Amazon, then get back to making money the next day.
Even if it was "only" 2x or 3x the expense to have a completely multizone setup, the ongoing operational burden is too high to justify over the 2, 10, or 100 year timeframe when no outages happen which could have been avoided.
Companies dependent on a single Amazon zone just give up and wait during a zone outage, blame it on Amazon, then get back to making money the next day.