I think you are understating the value of the redundancy available in Dante networks. I would never spec or install any Dante system without redundancy. The cost difference is really minimal even using good quality cable and network equipment. But the value can be huge when one of those devices fails. And two enterprise levels switches like the ubiquitous Cisco SG300 that only cost ~$200 each is a stronger and more cost effective solution than a single data center switch that costs $3,000.
I spec redundant Dante networks even for fixed installs for the same reason that I spec consoles with back up power supplies. Because spreading the load of fault tolerance over multiple points decreases the chances that a single point of failure will take down your show. If your primary network switch fails in the middle of a show, you can can’t pause the show for an hour while you switch it out and rebuild the hard patch. It’s an automatic roll over and you can deal with the equipment replacement the next day during your maintenance hours.
For the small individual end point devices like the AVIO adapters, you can easily have a spare or two that you can swap out in a couple of minutes if it fails. It doesn’t need to operate as a redundant solution because the ease and speed of replacement makes it less of an issue.
Even my personal six space recording rack has a pair of Netgear GS108T switches for redundancy built in to it.
