How cheap are they? How about the cheapest AMD-based Dimension E521 for less than half of the cheapest Core 2 Duo-based system. How about almost half of the cheapest Pentium D-based system? If you hunt long and hard you will eventually find the raw configuration pages, not the shiny bundle pages, and that is where the interesting stuff is.
Those pages are not flagged with bright orange "More value with AMD" labels, but the message is not lost. On those shiny ones, you can get an AMD-based system for about $200 less than Intel. When you look at the raw configuration pages, AMD here and Intel here, you can find the true prices. The cheapest I could make an AMD-based system was $279, that"s a Sempron 3400+; lose the modem, monitor and speakers while dropping RAM to 512MB. Upping the CPU to an X2 3800+ brings the total to $359. It"s hardly a screamer, but quite a workable office machine even with the Sempron.
For Intel, you can only go as low as $379 for the same configuration as AMD, but with a Celeron D 346. Upgrading to a Pentium D 805 or a Core 2 Duo E6300 will bring you to $559 and $759 respectively.
The low end Intel-based system is almost 50% more than the cheapest AMD-based system, and the cheapest dual core machines are at a similar premium. The cheapest Core 2 Duo is more than twice the price of the cheapest AMD dual core. These are not trivial differences.