This whole feature phone vs smarphone and firefoxphone vs android is a bit of a redherring. It is better to examine the capacity of the USD25 HW and figure out what can run on it.
Back in 2006 when I demo'ed a concept phone platform at the MWC, 500 Mhz ARM11, a VGA display and 128MB of DDR was sufficient to run our variant of the Opie platform, a Linux + Qt combo. Same Linux + Qt combo (which is what Tizen and Jolla's platform are at their core) runs well in a 500 Mhz Cortex 8 + 256 MB DDR2 today (I use this combo in OMAP3 processor based banking terminals running Linux apps).
The Spreadtrum platform is more powerful than this since an A7 will be faster than a A8.
Even an A5 is no slouch either.
Last time I checked a dual Cortex A9 combo with audio codec IC and power mgmt IC sold for USD7. A version with BB should probably be 10 for 2G. And these are at 10k volumes for a dual Cortex A9 that can run a 10 in tablet (I advise a mobile OEM, so these figures are accurate). A7 based parts will be cheaper since A7 is more optimal. Higher volumes prices on A5s and A7s can be significantly cheaper.
This will let it run a good optimized linux based applications, whether it be android, Qt or a run-time of your choice. Android may a little resource hungry but will take only a little more memory with probably another 200Mhz. In fact if I am not mistaken this HW is not too far from the original iPhone or Droid HW. Display quality will be poorer of course.
So as alex_m1 pointed out probably another USD5 in BOM. Assuming a generous 8% manufacturing cost, 40c extra for manufacturing. So we are talking about a USD6 spread.
So the vast price difference between a so called feature phone platform and an optimized android platform is a myth. The product price difference is due to positioning of the devices by the OEMs rather than indicative of major HW costs.
This implies that the mobile world is heading the PC way. For a vast majority of users, the low cost platform's capability has reached what a typical user wants. So faster CPUs buy you nothing other than greater battery life. And the everage user plays angry birds not a mobile version of an arcade game at 1080p resolution. Only component that has not reached commodity levels is good 720p/1080p displays. 4.5-5.5 in parts are still expensive and let us face it, for the vast majority of the users that this firefoxphone is aimed at, the phone will be primary internet device and a large display really counts.
I don't get why the big wow is about. Yes firefox uses lower memory, but the difference between that and a low end android phone(256MB ram and extra 2GB) is less than $5(according to DramExchange). Assuming the $25 is BOM we're talking about less than 20% difference.
Also, previous versions of android we're targeted at low memory and there are many apps highly optimized for low resources. For example opera mini(which is so light it can even run on feature phones), and FB plus for facebook, a facebook app that takes only 121k, Not forgetting the huge app ecosystem android have which some of it could be usefull for these phones.
So until a decent comparison is made between FirefoxOS and a well optimizised low end android phone, i prefer to stay skeptical.
JMO: I would say that Android phones will keep getting cheaper because there are so many competitors. Microsoft has to drop prices to compete with Android or their market share goes pffft. Apple can keep coming out with new models with incremental improvements and charge the same high prices, and their fans customers will keep coming back because you're not "cool" unless you have the latest model. The fact that they cost more makes them "cooler".
@Anand, that's a good question. I don't know what's going on with Windows phone, but as long as Android phones are concerned, that's exactly where they need to go if they are to proliferate in what used to be the feature phone terrritory.