For a while I did maintain a storage cluster that had close to 0.5 PB of data, and had a capacity of up to 3 PB (if you filled all the slots with the largest di

For a while I did maintain a storage cluster that had close to 0.5 PB of data, and had a capacity of up to 3 PB (if you filled all the slots with the largest disks you can buy). You want to ensure you have a lot of redundancy and spare capacity if you are managing it yourself. Luckily, the hardware is relatively cheap. It's the manpower that costs a lot. Still, I think it was only 0.1 FTE to manage this storage cluster, including the network, file systems, user access, swapping out bad harddisks and storage pods (but granted, it's I/O load was very light). Also, while AWS takes away the burden of handling the physical drives and the filesystem for you, now you have to handle interfacing with AWS. That means you need an engineer that knows how to integrate your application with AWS. If you can leverage more AWS services, maybe even avoid needing your own server rooms because everything is running there, it might pay off. European vs. American salaries might also change the equation. But if you just use it for storage, I don't think it's worth it at any scale.