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.