However I really wonder if he actually did any analysis on market sizing and if there is something preventing them to capture the share. I visited Gumroad website, explored it around and even signed up as user and still I have very little clue how exactly does it work. Yes, I can see it "helps" me sell something but I absolutely don't see anything available for purchase. There are no sign of marketplace. So where am I selling? How does the listing look like? What is exactly going on here? If myself as a geek can't figure this out within 30 seconds of landing, there is little hope for non-tech customers.
As an uninformed person in this domain, I think this market is huge. There are dozens of websites like Etsy enabling creators everyday and doing pretty well. However on those websites I know how exactly things works within a minute of encounter. On Gumroad, I can spend same time to encounter those annoying marketing jumbotrones that doesn't go in to any specifics. Being a lifestyle business is great and I love it but sometimes lack of growth is few simple issues like above and one should probably not confuse it with topping out market.