How many man hours should I ask for this almost-facebook clone?

Question

I am asked to prepare estimates for an application with the following must-have features.

1. Login, including several hierarchical user access levels.
2. Chat amongst users allowing the user to become invisible.
3. Ability to post a public message, video, voice recording, image or draw an image using flash based sketching environment.
4. Ability to like/unlike posted messages.
5. Ability to comment over it.
6. Ability to close this message for comments.
7. To Tag messages, images and videos posted.
8. To build communities and have forums there.
9. Standard social networking features such as having friends/following some user's messages (like twitter). Sending private messages and so on.
10. A developer API like Facebook.
11. CodeIgniter must be used for this.

I don't expect any SO user to do my work for me. I am just looking for experienced programmers who can look at this and give a lower bound for the estimates.

My guess is this would take 5000 -7000 man hours to design, develop and test.

Answer 1

wow this is serious business, and a simple answer can't be given here... Sit down with your crew and brainstorm is my advice. 5000 to 7000 is a big uncertainty for this company... 2000 difference (about 40%)?