Today marks the introduction of the Nvidia GeForce GTX 1080 Ti, with the same high-end GPU as the Titan X (Pascal), but cheaper. You can read all about this new card in this article, including benchmarks for both single-GPU and SLI.
About nine months ago Nvidia released the GeForce GTX 1080 and 1070 cards, based on the GP104 GPU. This is a mid-range GPU, with a die size and memory bus comparable to mid-range GPUs of previous generations. However, since AMD had no product with comparable performance, nothing stood in the way of Nvidia charging high-end prices for the GTX 1070 and 1080.
Meanwhile, Nvidia did introduce the Pascal-version of the Titan X, based on the GP102 GPU. This card was Nvidia's fastest GPU, and it was also extremely expensive. The release of a GTX 1080 Ti, with the same GPU but some differences, at some point in the future would not be surprising. After all, this is what we have seen for some generations. That point is now, probably not very coincidental, since there are some noises about AMD introducing a new high-end card (Vega).
If we compare the GeForce GTX 1080 Ti with the Titan X (Pascal), we will see that they have just as many shader units. This is surprising, because manufacturers usually disable shader units for market positioning. This is not the case with the GTX 1080 Ti, as it has 3584 cores, like the Titan X. The GTX 1080 Ti even has a higher clockspeed: with a boost frequency of 1581 MHz, compared to the 1531 MHz of the Titan X. The difference is that the GTX 1080 Ti has fewer render output units. These units send the pixels to the memory controller. This also results in a memory bus that is less wide: 352-bit, compared to the 384-bit of the Titan X (Pascal). It's for this reason that the GTX 1080 Ti has an 'illogical' memory amount of 11 GB, where the Titan X had 12 GB.
These are not the only differences between the cards. A significant disadvantage of the Titan-cards is that they are only released as reference cards, or Founders Editions (as Nvidia is calling them since Pascal's launch). The cooler of the Founders Edition produces a significant amount of noise, and also does a less good job cooling than the custom coolers that partners put on their cards. This limitation does not apply to the GTX 1080 Ti, which means that you can get the card with a cooler that is a lot better - unless you are planning to put the card in a custom watercooling loop, of course.
The original Titan (Kepler) had the advantage that it did a very good job with double precision floating point calcuations (FP64), which are often used for scientific purposes. The ordinary GeForce GTX 780 and GTX 780 Ti had been very limited in their FP64, because this part of the GK110 (the same GPU used for much more expensive Tesla-cards) was disabled for these cards. This was not the case with the Titan, which used the same GPU but did not have this FP64-handicap. This made it an attractive alternative for the much more expensive Tesla-cards. However, the Titan no longer has this advantage starting from Maxwell-generation.
Maxwell was purely aimed at gamers, which means that it had severely limited FP64-performance to begin with. The only reason to buy the Maxwell-generation Titan X, was to get its very high performance a few months before the release of the GTX 980 Ti. The same is true of the current Pascal-generation: Nvidia produces the P100 for workstations, a card that is the equivalent of the GP102 for gaming purposes, but with a lot more FP64-units. The GTX 1080 Ti that has been introduced today makes the Titan X (Pascal) obsolete, because that card is a lot more expensive. The GTX 1080 Ti would even be preferred at the same price point, because of the custom cards that ensure less noise, better cooling and thus more consistent performance.
The GTX 1080 Ti has an MSRP of $699, for both custom cards and the Founders Edition, significantly less than the $1200 you would pay for the GTX Titan X (Pascal). In order to not hurt the sales of the GTX 1080 too much, Nvidia has cut the price of the GTX 1080 by between $100 and $150 - from $599 to $499 for custom cards, and from $699 to $549 for the Founders Edition. Meanwhile, the price of the GTX 1070 has been cut by $50, which means that you can purchase one for $399. These cards remain rather expensive, but the launch of the GTX 1080 Ti unquestionably means that you can buy a lot more performance for (about) the same price.