this chip has features disabled to clear not let it allow to compete with K20X.
http://www.anandtech.com/show/6760/nvidias-geforce-gtx-titan-part-1/4
"NVIDIA has stripped GK110 of some of its reliability and scalability features in order to maintain the Tesla/GeForce market segmentation, which means Titan for compute is left for small-scale workloads that dont require Teslas greater reliability.
ECC memory protection is of course gone, but also gone is HyperQs MPI functionality, and GPU Directs RDMA functionality (DMA between the GPU and 3rd party PCIe devices). Other than ECC these are much more market-specific features, and as such while Titan is effectively locked out of highly distributed scenarios, this should be fine for smaller workloads."
It does not cost Nvidia much to enable full 1/3 speed DP processing as in GK110 Tesla.
But the other point that you raised is very important. a 3GB Titan with 1/24 DP only and a better price at USD 650 would really make an outstanding product for gamers.