There are two reasons why AMD CPUs are much cheaper especially at the high end...
1 - Intels high end processors are better than AMDs high end processors
2 - Intel charges way too much for their products (bear in mind I have no idea how much it costs to actually produce a single processor)
That being said the best available AMD CPU is really enough for the most demanding games currently, you will find the the I7 range of CPUs really excells at things like 3d rendering in things like Maya and ZBrush and profession programes such as Photoshop and the like.
As far as a GPU is concerned AMD is much more competative and in many ways actually better, particularly with DX11 so a card like this http://www.newegg.com/Product/Product.aspx?Item=N82E16814127581 is a pretty good option.
