I think tptacek's point wasn't about Gates's wealth, it was that Starbucks at the time was pretty tiny. It (Starbucks) has a kind of interesting history, tangled up with Peet's Coffee & Tea in its very early years.
(Starbucks also used to be a lot more, well, serious about coffee, selling fresh-roasted coffee in bins in the store rather than bags shipped out from central roasters, as well as selling a small but well-curated selection of brewing equipment that wasn't just Starbucks-branded stuff. Peet's still has some of that vibe, although they're less eclectic now than they were even 15 years ago.)
(Starbucks also used to be a lot more, well, serious about coffee, selling fresh-roasted coffee in bins in the store rather than bags shipped out from central roasters, as well as selling a small but well-curated selection of brewing equipment that wasn't just Starbucks-branded stuff. Peet's still has some of that vibe, although they're less eclectic now than they were even 15 years ago.)