Groucho:

 

 

 

I think I've seen something similar online and was way over my pay grade but agree with you.  Xero with their 862,000 subscribers probably can't justify the expense unlike another AWS client calling themselves Netflix whose "NZ content" is streamed from a lot closer to home.

 

Expense varies with the level of redundancy you want:

• "Cold", where you have a backup of your data and server images outside the region in something like AWS Glacier, wouldn't be too expensive. The time to get the environment running could be days, it depends how much preparation is done.
• "Pilot light", where you have a minimal mirror environment running and can scale it up, costs more, but not too much.
• "Active - active", where services run across two sites, is more complex and expensive, with data synchronisation issues. You also have to decide whether you size each environment for the full load in case one fails or half the current load with the ability to scale if one site goes down.

Highly critical things like NASA mission control and anything where lives can depend on it might use multiple active sites. Accounting software, well, customers can probably wait an hour for it to scale up.