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 ever reach this level then we're on MAR!....forget MOON!