The most interesting thing about the setup premise, is that it should have a "yet" attached to it somewhere.
Unless something terrible has happened in the last few months, their recent November 2018 numbers indicate that at a continued reasonable rate of growth over another decade, they'll have a sizable business and a large number of creators utilizing it (which is one of his goals). It would be worth at least a hundred million dollars. If the growth spikes upward even a bit on average (maybe they garner more interest with scale or the market expands faster), it could get them to between a $500m and $1b valuation a decade out. Modest compounded growth with even a small kicker, from where they're already at, will produce a big outcome over time. So he'd be a sub 40 year old with an extremely valuable company and a lot of people that use what he created (and which I assume he owns a large part of at this juncture).
Given time and their history of slow but steady growth, Gum is more likely than not to produce a homerun. The continued growth over many years is a stellar signal that they're already winning as a business. You can get there slow or fast. The VCs want it fast, Sahil can afford to take his time, he's still quite young and Gum is his.