It doesn’t look like a mistake if the title and post both say 1 million users. Anyway, you should change the topic title from “1M user at the same time” to “1K user at the same time” so you might attract someone with a similar load who could tell you what they are actually using. By the way, what is a “RAW server” - did you mean “RAM”?
Your assumption of a blog should be ignored because the forum should make higher demands on the server. But you still have to consider what users are actually doing:
anonymous vs logged-in
read vs post
There are a lot of useful topics about capacity and scaling in the #hosting category. Here’s two guess-timates that may be in the same ball park:
But above those levels, there is this site that was running on 8 CPUs and 16GB RAM:
What service level(s) are you aiming at? This post/topic is my favorite because it compares Discourse with traditional (i.e. LAMP-based) forums:
Don’t forget that if you are cloud hosting then the size of the database becomes more relevant because you might have to spend more money to expand limited storage.
FYI, here’s some further info which might be relevant to your decision-making options:
You can simulate capacity on a Discourse site and see what happens: