In my case: I did the math and it would take me ~4-5 years to recoup the initial investment (of about $450) in my homelab (comparing my server + 3 copies of 2TB with the cost of a 2TB google drive subscription). (Also excludes the time spent building the server, and I found very good deals; if you get a regular NAS this becomes about ~10 years)

There is, however, a fixed component cost to building such a setup that gets amortized the more disks you buy- I believe it becomes worth it to use a NAS cost-wise over about ~5-6TB of data (and definitively worth it when you get into the tens of terabytes).

Or if you need low-latency storage / any type of performance - neither the cloud nor my homelab has removed my need for my portable NVMe drive