As of April 1, 2012, Microsoft has a new SQL Server 2012 Core Factor Table for AMD processors. You can download it here (PDF warning). The complete SQL Server 2012 Licensing Overview is here. The most relevant part of this table regards the newer AMD 31XX, 32XX, 41XX, 42XX, 61XX, 62XX Series Processors with 6 or more cores, that have a core factor of 0.75. This means that AMD cores are somewhat more affordable for SQL Server 2012.
Back in January 2012, I talked about a new Hewlett Packard TPC-E benchmark submission that showed a 1,232.84 TpsE score for a two socket, 32 physical core AMD system, compared to a 1284.14 TpsE score for a two socket, 12 physical core Intel system. Both of these TPC-E benchmark submissions were on SQL Server 2008 R2. Back then, I pointed out how you would be paying 2.66 times as much for SQL Server 2012 Enterprise Edition licenses for the AMD system compared to the Intel system (32 physical cores vs. 12 physical cores).
Now, with the SQL Server 2012 Core Factor Table, you would only be paying twice as much for SQL Server 2012 Enterprise Edition licenses for the AMD system compared to the Intel system (32 physical cores times 0.75 vs. 12 physical cores). That is a slightly better story for AMD, but it is still a pretty hard sell. Based on the TPC-E benchmark results, both the older Intel Xeon X5600 Westmere-EP series and the new Intel Xeon E5-2600 Sandy Bridge-EP series do much better per physical core on OLTP workloads than the latest AMD Opteron 6200 series processors. These Intel processors simply have significantly better single-threaded performance, which is very important for OLTP workloads.
I really hope that AMD can do better with the upcoming Piledriver core based Opteron series in 2013.