That's not quite the case.
Cerny said "that for 12 channels, 825 GB is the most natural choice."
He said that before going into the discussion about the sweet spot.
The reason why is because chips are made in multiples of 2: 2 GiB, 4 GiB, etc. The PS5 is using 12 64GiB modules. The next step up is that 12 128 GiB modules.
Note that 12*64GiB = 768 GiB = 824.6 GB.
For 1Tb only if perhaps Sony have a smaller SSD soldered on the board with slower speed but just for OS and apps.
duduspace11 "Well, since we are estimating costs, Pokemon Red/Blue did cost Nintendo about $50m to make back in 1996"
Mr Puggsly: "Hehe, I said good profit. You said big profit. Frankly, not losing money is what I meant by good. Don't get hung up on semantics"