That's editorializing.

For many sites, a single server in a single zone (e.g., a non redundant server, an instance, a slice, a VM, whatever) is the right decision for ROI.

For many sites, the money spent on redundancy could be better spent on, say, Google Adwords, until they're big enough that a couple hours downtime has irreplaceable costs higher than the added costs of redundancy (dev, hosting, admin) for a year.