generally speaking, the marketplace isn't receptive to low-end manufacturers who try to go upscale--think hyundai trying to sell luxury cars. kz does a fantastic job at the $10 pricepoint--i'm positive if their iems were positioned at the $50 point this thread wouldn't be a thousand pages. ergo, a $100 kz will be quite a curiousity, but you got to wonder if they'll sell a ton of them.
I really see no reason not to give KZ the benefit of the doubt when everything that's been fairly 'premium' i've had from a 'premium' manufacturer has turned out to be significantly flawed or an outright pile of crap.
Sony cables become brittle in the cold and snap in half. My XBA3s suffered this fate. a few weeks later they were no longer usable.
Then i got the mdr-1rbt - it had a plastic construction headband that developed cracking over time and were unusable in 6 months.
Had a simillar experience with AKG. their K550 was really good until the weak plastic joints of the headphones gave way and the pads tore because faux leatherette disintegrates.
Then there was the Grado SR325i - the most uncomfortable pair of headphones i've ever owned. Still, it was better made than anything i've had previously.
Then i got the T50RP MK3, which arent as transparent as i'd like them to be but atleast they're built like a tank. I still have these.
That being said, i got the KZ RX about at the time i got the 1rbt and it's still kicking. And it has a kickass sound for $8. The ZST goes up against the XBA3s and K550s for $12 in terms of SQ.
Now i've had 2 critical failures with KZs. my ATE's jack [Which was sortof my fault] and my HDS3 at the joint [which it more sortof wasnt], and some QC issues [Cracking drivers when pushing on seal, no seal on one channel]. Those i could both take responsibility for (sleeping with HDS3, accidentially tugging on ATE ). Nothing feels like it'll fall apart as with junk earbuds or deliberately designed to fail in a very specific manner.
I dont feel like there's a faustian bargain, like when i go Sony or AKG or Harman because if it works it'll just work, flawed as it may be. Even if the ZSR is way more expensive it seems KZ has earned my consumerly trust with what they've put out so far.
That being said, all of my above experiences make me a huge KZ fanboi, so you could say im biased now lol.