Since the article you point to is about programming then I'd assume your asking about the technical side of things rather that actually acquiring 5-10k users (which is very difficult). It's an interesting question, but as you have it phrased it's similar to "how long is a piece of string."
Firstly, the load of a web app is going to be dictated by what the app actually does.
Also 5k-10k users should be clarified as to whether you mean total users or concurrent users. Testing capacity can be actually tricky figuring out how the number of users equates to actual hits to your servers.
As an example, we have nearly 50k accounts but on average only a few hundred are using the service at the exact same time. I would guess that our app is fairly complex compared to the average app. We run 3 app servers, 1 DB master, 1 DB slave, and 2 cache servers. Our monthly hosting bill is around $1,200.
Firstly, the load of a web app is going to be dictated by what the app actually does.
Also 5k-10k users should be clarified as to whether you mean total users or concurrent users. Testing capacity can be actually tricky figuring out how the number of users equates to actual hits to your servers.
As an example, we have nearly 50k accounts but on average only a few hundred are using the service at the exact same time. I would guess that our app is fairly complex compared to the average app. We run 3 app servers, 1 DB master, 1 DB slave, and 2 cache servers. Our monthly hosting bill is around $1,200.