This is why you shouldn’t roll your own hardware (unless you have very, very specific needs).
What concerns me, from the image, is that they seem to be using cheaper, consumer grade drives (Samsung 860 PROs I assume). This is asking for trouble - as they went through - 3 drives failed simultaneously. I've only ever dealt with Cloud infra, but even I know that drives that are bought together, tend to fail together. It's likely their new batch of drives will also fail simultaneously - backblaze has done a ton of research on drive longevity.
Just seems penny-wise, pound-foolish to me.
It's exactly the same as the lights in your house, all of these were made at the same batch with the same quality of material and used the same way, they tend to fall apart within a few days from each other.
My guess is that it would have been a tiny fraction of their cloud bill, and their downtime would have been a smal fraction of the colo downtime.