TXP performance is high end and competing with it first or last makes no difference in regards in how much market share it will gain AMD, that amount of cards AMD sell at the price bracket is insignificant so gaining market share should not even be mentioned in regards to it.
Price to performance only mattered to people who only care about price to performance and nothing else and in the enthusiasts bracket that is not the case.
For example the average person who is willing to drop a more than average amount on a car is not going buy a Car with Skoda on the grill even if it was slightly faster than all the other cars in that price range, they just don't have the brand image to get many people to buy it and yes a one off was made which was really a Audi R8 remodeled.
The higher you go up the price bracket the more the brand image matters.
AMD has to sort out its.
Brand image and Marketing which is light years behind Intel and NV, many don't want to drop large sums on a lesser image brand.
Get rid of the Driver stigma which is still perpetuated with no matter how bad NV drivers may be to an individual, the individual said "Im going AMD" and the reply was "don't go AMD there drivers are even worse".
Then you have PhySX, G Sync, Shadowplay ect... many swear blind all theses are worth paying more for then AMD equivalents even if the GPU they have bought is bad in price to performance to the nearest AMD card.
The Rx 470 vs titan 6gb thread, the power of Brand image and status right there when it comes to the Titan recomadtions
https://forums.overclockers.co.uk/showthread.php?t=18750268.
When AMD gets that all sorted then they can make worthwhile in inroads at the higher end price bracket.
Getting people to changed brand when they have been loyal to another for many years is can be extremely difficult unless the other brand screws up big.
Get the new people who have yet to become loyal and thats starts at the cheaper end but that still requires good marketing at the very least because even an inferior product with the right marketing can out sell the other as people dont do enough independent research and the superior marketing is all they know hence why when i was getting ready to build my first PC all the enthusiasts i personally knew told me to get a P4 and a NV card but i did my research online first, AMD had the better performance and ATi had the better image quality at the time in desktop and gaming after reading a lot of reviews.
So AMD cards in the £450 and up will hardly make a dent when it comes to market share until they tackle what i have mentioned or unless they have something really special and the biggest thing that is helping AMD at the moment is Dx12 and Vulcan and arguably the Console connection and the drivers stigma is starting to subside slowly.