I think it comes down to supply and demand, my guess is that Komputerbay pays about the same price for a 64gig chip than they do for an 128gig one so the price difference is relatively minor.
I'm one of the lucky people (knock on wood) that got two very fast 64gig 1000X Komputerbay cards a few months ago. I really need more cards, but weirdly enough I prefer 64gig over 128 since it forces me to not rely too heavily on a single card should something go horribly wrong.
It is likely that the chips of the 1000x 64gb, 1000x 128gb and 1050x 64gb are exactely the same.
At the current nm proces there are many flaws on the chip and when they do quality control they check how much of the surface is usable.
Then they upload the right firmware deciding size and speed.
http://www.bunniestudios.com/blog/?p=3554Same thing happens with cpu's. There is no difference between an intel 2.0ghz and a 2.4ghz.
The 2.4 just met a higher quality standard and is therefore capable of handling the 2.4ghz load.
So the 1050x cards are probably just 1000x cards which have showed to run at 1050x during quality control.
Maybe the manufacturing proces improved and their yield of 1050x cards increased.
But because not every chip gets checked (only a sample of each batch) you might get a very good 1000x or a bad 1050x.
If it were up to me I would wait until a new generation of chips come out.
Unless if you have cash to burn now and need to be a bit more sure you get enough speed, but like I said there is no way to know.
Would be interesting to know if maybe the controller changed, but because it is only a 5% bumb it is more likely an improvement of the yield.
(you also see intel doing this, between refreshes they often release chips with a minor bumb of 0.1ghz, this is also because of improved yields)
