Dave was not just talking about the CPU. He was talking about the total build which would be CPU and motherboard (keeping everything else the same). Motherboards for Intel with similar features and specs tend to be $40 to $70 more expensive in price. So you are looking at an AMD system for $379 for CPU/Motherboard and Intel for $550 which is then closer to +70% price difference.
Oh, he didnt mention that in PM. In fact he stated he used his LOCAL pricing compared to I'm guessing the MSRP (which isnt a fair comparison IMO - MSRP or big vendors or bust).
Also, I think your math is incorrect... 379*1.45= ~$550. So its 45% more than the AMD system, not 70% more as you stated = 379*1.7= $644.xx.