Create/design a virtual online world!

I need to know the estimated price for creating/designing an online virtual world with everything it needs. In this world anyone can register and log in and then interact with other people online. As an example for what I need (but at a little scale) you can take a look at [login to view URL] . This should be the main idea of the website/virtual world. As a conclusion I need YOU to tell me an estimated PRICE, how much time will it take to accomplish it and what are the "things"we need in order to do it functional. (scripts, hosting, etc.) Hope to hear from all of you that knows about this!