I think an understated point is that scaling changes costs both ways. A mode of operation that is cost-effective for netflix or google is likely going to be pro

I think an understated point is that scaling changes costs both ways. A mode of operation that is cost-effective for netflix or google is likely going to be prohibitively expensive for a small start-up. At a sufficiently large scale any constant factor overhead is negligible, big-O is all that matters. At a small scale, the constant factor can drown you. It's a very common trap to design a system with technology that could scale to a million users, but without being able to afford the servers so it sort of struggles to serve even a hundred users.