How much does it cost to host a Joomla/Drupal site in Amazon AWS?

I want to host a Joomla (or Drupal, haven´t yet decided) based website in the cloud. How much would it cost to do it with Amazon AWS or another cloud computing platform? I am very new to cloud computing, but I consider myself an advanced PC user, and I could, say, work a little harder in implementing the cloud on independent hosting sites in South America, where I´m based, I see there is the need for some queue. I’m pretty much padawan at this. My TLD is a .org. I very much unnapreciate RoR so heroku not an option.
Having faith that my question will be read and answered, I thank you in advance.

I don’t know much about cloud computing, but 2 minutes after reading your question I happened to stumble across this guy who seems to be doing the same thing:

http://millwoodonline.co.uk/vpsnet-turnkey-linux-drupal