This has been answered many times, maybe browse the forums for a few minutes before posting a question, you might be surprised at what you find. The Model B is $35, the Model A is $25, and the model A is not being manufactured or sold at this moment. There is no given date for when they will begin to manufacture and distribute the Model A boards. There is more information about this in a few topics on the forum.
I wouldn't be surprised if this topic is locked as this question has been answered so many times, I'm just warning you.