What % of AT&T's market cap ($175B) is its SMS business? What % of Lockheed Martin's market cap ($65B) is its space business? Think about the incumbents WhatsApp & SpaceX are trying to dislodge. Generally speaking the ones WhatsApp (now Facebook) are larger by market cap than the ones SpaceX is targeting. That reflects the fact that something everyone uses a little bit every day is generally worth more than something used by very few people, intensely.