Wait just a minute.... Why are people saying that the X2's are more expensive than the Pentium D's??
I had a quick check on prices in the UK, and well if you want to be picky about the subject then yes, X2's are more expensive.
If you look at the bottom end of the line for both AMD and Intel, then the AMD 3800+ is around £225, and the Intel Pentium 4 830 is around £205. For the huge amount of extra performance from the X2, I'm sure people can stretch to that extra £20!!
Also, at the top end of the line, the AMD 4800+ is around £550, and the Intel Pentium 4 Extreme Edition 840 is around £630. So actually Intel are charging more for top end CPUs, and AMD are charging minimal amounts for their bottom end.
Here's where I got the prices from:
Intel -
http://www.overclockers.co.uk/acatalog/Intel_Pentium_4_Dual_Core.html
AMD -
http://www.overclockers.co.uk/acatalog/AMD_64_X2.html
So AMD have better performance, and charge SLIGHTLY more than Intel but yet out-do to the Intel in multi-tasking!!
Stop saying AMD are more expensive!!
EDIT: All prices exclude VAT by the way