1000 TPS is a theoretical number, in fact I'd wager that it would take at least 2 (possible more) years to have that many transactions per second. So no, you won't need 300GB available (per month).
Reaching it may be possible but to sustain it over a long period of time would be something else.
31 billion transactions if we could maintain 1000 TPS for a year.
If we every reach this level then we're on MAR!....forget MOON!You get the causality wrong.
Let me explain:
One idea of Nxt was, theoretically, to be able to handle 1000TPS. To dethrone VISA maybe with their bullshit high fees. Some small shop owners lose 50% of there marge today because of VISA. Think about it.
Now, Nxt is the saviour. If we want to get to the Mars/Moon, there needs to be something like "well, no problem, we can easily handle 1000TPS in the future if we want. Just some coding and done". <- This maybe leads to 1000 TPS in the future -> to the mars in the future. Not the other way around.
btw visa handles 2000 TPS on average I believe.