I guess you have to be an optimist in his line of work.
He's all-in on the global warming hoax, so I wouldn't call that optimism, so much as gullibility.
SpaceX's BFR rocket system is expected to have capabilities for interplanetary travel, and be fully reusable. A flight will cost less than the initial Falcon 1 flights, which Musk pegged in the $5 to $6 million range.
OTOH, that's pretty optimistic, right there! :^)