Still cheap, but not that cheap.
If you have two tiers available, someone will use the less reliable one because that’s how they fit their budget but then because it’s “in production” they’ll expect the same level of service.
All of these are manageable but what you’re really hearing is that the technical issues are really the tip of the social iceberg most organizations have. One of the reasons people pick AWS isn’t just that it’s usually cheaper than the full cost of rolling your own but that lots of these things don’t affect you: you never fail to provision an EBS volume because the VPs of finance and IT are still arguing about procuring a new rack of disks, people can’t request endless customizations because the options are “take it or leave it”, etc.
There is absolutely no technical reason to provide all of your storage needs with a single quality of disks. You may do that to get some economies of scale, but if the impact is that high, you should rethink it. You can just as well have two different solutions, one with a huge amount of disk space, little redundancy and low performance, and one with a limited amount of space, plenty of redundancy and high performance.
And yes, I know that goes against every common ops procedure, because disks are so cheap. But the next thing you hear is always that disks are not cheap at all, and you really can't have it both ways.