Actually Titan is overpriced for a reason.
That is that Titan is designed to be SLIed.
You can easily see that it has the best blower available for any GPU in the world and also the fact that Blowers work much better than fans in SLI / XFire.
No one would buy such a powerful single card when same company has 50% more performance in GTX 690 which also costs same.
Usually people buy 3 Titans for Tri-SLI since 690 SLI can give 70% more performance than GTX Titan SLI.
Its more of rich people's card of choice.