Earlier quoted context omitted.
>That number will obviously depend on the read/write ratio of any given website; but it's hard to imagine any website where that number is actually "1". I can imagine a static website where the content is read-only for users and is only editable by admins/developers/content managers through some CMS.
That'd be a near-infinite ratio. The parent is discussing a site where the ratio is near 1 (i.e. roughly as many reads as writes).
Suppose, on the other hand, that a single user generated around a 1% write utilization when they were actively using the website (which still seems pretty high to me). You could probably go up to 120 concurrent users quite easily. And given that not all of your users are going to be online at exactly the same time, you could probably handle 500 or 1000 total users.