generally, a intel i7 build costs about $200 more than an AMD phenom II ( X4 or X6 ) build. the ram, motherboard and the processor its self is more expensive with intel builds.
Building off what Sean had said, AMD (X4 or X6) Builds generally run $200 Cheaper than a Quad Core i7 Build.
X6's are 6 core processors that run from $200-$300 while Intel's 6 core i7 is a whopping $1000...AMD will most likely be the "Better Bang For Your Buck".
now some of what they where saying could be taken the wrong way. you can build the amd cheaper, the intel will be faster for a little more "best bang for your buck" is all up to how much you want.
if you ask me, its worth the little extra for intel setup (unless its going to force you to cut cost some where else)