ya just gotta know where to look

I can still get em
probably will for a little while longer
(at least until 2014)
most times an Unused OEM COA comes with older hardware
and usually cost less than the OEM System Builder media would cost
and they're usually unused because the original installation was VLK
and the OEM Supplied COA was there just because MS said it had to be there
eg.
right now I can get p-4 systems with unused XP-Pro COA for under $100.00
so I get 1 COA at a discounted price and free hardware to go with it

if you want a little newer like core2duo it's about $130 - $160
thus the hardware is still free or nearly free
as the XP-Pro system builder kit with 1 COA & CD was around $139.00