Almost identical specs as a Lumia 520, too. 4 GB storage instead of 8 GB (both extensible via sd). Even for a low budget phone, I don't get why they don't go with at least 16 GB. 4 GB is pathetic.
It's even closer to the Nokia X. Once you've installed Google Play that's not bad, and abroad you can pick up the dual SIM version.
The Nokia Store is missing pretty basic apps so provides a selection of third party stores for you to install. Alternatively you can sideload Google Play services.
Here in Czech Republic (which is semi-eastern europe), Lumia 520 is 50 % more expensive than ZTE Open C, and 8 GB Moto G is twice the price.
Now, Lumia 520 has better camera and perhaps better screen and CPU, and Moto G is whole different matter (720p, quadcore, 1 GB RAM), so the prices make sense. The cheap Chinese devices that you can get for the same money (like Huawei Y330) have generally the same hardware, so I don't think ZTE is overpricing the ZTE Open C.
So, while I can't give you prices, it's possible that the ZTE Open C is more competitive in markets like Eastern Europe or South America.
EDIT: the reason to get ZTE Open C instead of say, Lumia 520 or Huawei Y330 would be that FxOS devices should have better browser performance for the money, at least from the impressions from the SVG comparison video, and the browser seems to be much better integrated to the system than on Android or Windows Phone.
I was unaware you could run Firefox OS on a Lumia 520. Do you have a link that describes how to do that? Or is there a vendor selling Lumia 520's with Firefox OS? I also have not seen Moto G's running Firefox OS.
EDIT: Possibly I should add some context to my question. I'm not sure why the comment is comparing a phone running a different operating system and different software. So I thought maybe these other phones could run Firefox OS and I just didn't know. I've been using Firefox OS for about a year and would not want to use a phone on a different OS. The article was about a new version of a Firefox OS phone.
At the bottom it lists the support and I see all browsers with "Not Supported" and then this line "This API is currently available on Firefox OS only for any installed applications."
Do the "principles" in your case revolve around openness, freedom, and so forth?
I've heard a lot of people use such ideals when advocating for Firefox OS, but I just don't see it all holding true in practice.
Firefox OS is one of the more restrictive environments, at least for developers. I'm basically stuck using JavaScript, HTML and CSS. If I want to use any other language, I have to try to molest it through something like Emscripten. If I want to create a native app, I'm out of luck.
At least a platform like Android gives developers a comparatively wide variety of options, from Java, to C and C++, to JavaScript/HTML5/CSS.
By limiting the freedom of developers to create apps as they see fit, then it directly impacts the freedom of end users to use such apps.
And I don't see Firefox OS as being particularly open in other respects. Maybe the code is available under an open source license, and maybe Mozilla will accept minor bug fixes from the community, but I really doubt an average user would have any ability to influence/impact/control Firefox OS beyond that. Decisions are foisted upon the users. It doesn't seem any better than Android, or iOS, or whatever other platform you want to consider.
The same goes for the "But we implement open standards!" claims. The process to come up with such standards isn't very open at all. It ends up being controlled by a small handful of major browser vendors, with minimal to no input from others. Merely being published does not make a standard "open".
All in all, it makes no sense to me to choose Firefox OS on a matter of principle. It doesn't actually meet whatever standard is being set by those principles, yet it still gives a much inferior experience to the alternatives.
There are different kinds of freedom and openness.
FxOS is made by Mozilla, which is very different in both goals and culture from Google, Microsoft and Apple. You don't need special account with OS vendor to unlock full functionality of the phone like with Android and WP, or to even use it at all as with iOS. You don't need special license (that actually costs money, IIRC) to load you own software to your own device like with iOS or WP. You can develop the software for FxOS on any operating system, unlike with iOS and WP.
This is different kind of openness than "can I use C", but to me it is more important. Personally I hate Javascript with strength of thousand suns. But FxOS seems to be worth the price.
I can't see it selling here.