The deal with GPUs is similar as it is with CPUs. As one article here on Tom's states (Best CPUs for money), there is little reason to buy a cpu that costs over 200 pounds (or was it dollars?) if you want best value per money payed. Same applies to GPUs. Pay 300 pounds worth a GPU, and you will get a piece that provides 60-70 per cent of performance (not actual statistics, but to give you an idea). So by this a GPU that dishes out all 100 of performance should cost around 500£... when it fact it costs double that (Titan, 690gtx etc). What this means is that past certain point you do not pay that extra money for increased performance directly. You pay increased price for every per cent on top, which means one thing - it becomes a privilege to own a top-of-the-line GPU. Do manufacturers benefit? Hell yes they do. Do consumers benefit? Hard to say. See, this opens up a whole new window of opportunities. In example, it becomes debatable what level of performance you will be satisfied with. Can you justify paying a thousand pounds for the best? Or will that mid range GPU for 200 will do just fine, with some settings set to medium, some to min, and a 720/1080p resolution instead of 1440p and beyond? Both AMD and Nvidia seem to pay more attention to this mid range market, as you may find awesome cards that deal with current titles just fine, provided you "limit" yourself to one screen and deal with a few compromises. GTX 770 arguably one of the best GPUs for the money. Radeon R9 280 should not be too far behind. Imo manufacturers recognise this mid range segment and its popularity thus providing us with more options.
In the end, there's a third factor that weighs in. Popularity. This happened with newly released Radeon R9 series. It became very popular among Lit/bitcoin miners (don't ask me i'm not into that stuff) and they wiped the selves clean real quick. What do the manufacturers do? Raise the price, because why the hell not if people are still buying those. So there you have it. Guys that replied earlier touched important points of what modern GPUs provide us with and that's, personally, something worth paying the money for. How much? Well that's, my friend, for your judgement and pocket to decide 😉