Here is what I came up with as far as distribution of parts. In short, there is a lot of downbinning going on with SC A64s and Semprons, less so on X2.
The first column is the price of 1 unit box unit from NewEgg.com. Second column is 75% of that, which is what AMD may actually get, assuming distribution costs, shipping costs, NewEgg Profit, cost of returns etc.
My guess is that OEM are buying tray parts for about 75% of the list outright. On single boxed parts sold through distribution and resellers, there is about that much overhead.
It is just a WAG. I didn't really do Opteron, since there are just way too many parts. I think I may be too low on Opteron (as far as revenue contribution).