How much does a web server costs to run?

Hi guys, this is one of the most useful sites ever visited, so hope you guys can help me with this question...

My question is regarding (Web Server / Web Hosting / Dedicated Servers)

How much does each one of these costs, for example; how much it costs to run your own web server, and what are the requirements for that, like what do we need to setup a web server from scratch? If you know what I mean...!

The second one is web hosting, how much does that costs to hire a good reputation hosting, please consider the security and backups?

And thirdly, how much it costs to hire dedicated servers, if you know any good ones, please refer them...!

Please reply me ASAP, I need to run a website within a day or two, so must know the advantages, disadvantages and costs of each?

Please reply, I really need help on this.
Thanks in advance, hope you would all understand what I have written above.
Regards, Daz, London