The premium plan from Google has 2 TB and costs about the same annually as the electricity for the NAS that the GP comment suggested for comparison (at 100% usage). So at the same ONGOING cost (not even counting initial investment), the NAS has 8 times more storage. 16 times if you assume it will be mostly idle. Except if you want high availability with RAID, then you're back to 8 times. And haven't yet thought about backups.

All this assuming that you even need that much storage, which most people definitely do not.