This blog is credited to Program Manager Anton Kucer in our Media services team. I learnt a lot pricing detail from a email conversation with him. If you choose to use Windows Azure Media Services, here is a detail explanation of what you will need to pay. Also, it provides some guidance on how you choose right amount of services such as # of reserved units. If you have more questions, please put your comments below and I will pick them up into Q&A section in this blog.
These are pricing details posted on official Windows Azure home page. Please read the official post first and if you still have questions, read this blog which is my best effort for explaining pricing. As said, if you choose to go through general media workflow (encoding your content and host them for streaming purpose), you will incur 4 types of costs. Read More Here