Maybe they just don’t need too much storage since they expire quickly. This would be an interesting thing to graph, if they release the statistics.
Mozilla has quite a bit of money, most of it from their default search engine deals. I'd wager to guess that most of it goes to wages.
Net income 2017: 89 million.
Not that much for a company employing more than a thousand employees. But impressive for a corporation that is 100% owned by (and allegedly managed like) a non-profit org.