Yeah, if you don’t get the choice of (or choose not to want) carrier subsidies, then it is a huge investment, and I can see why a replaceable battery would be essential (because the life of your device might be longer than the life of the battery).
I think that the reason so many phones don’t bother with replaceable batteries are that the majority of people do get carrier subsidised phones, and therefore get a new one every couple of years, so the battery being dead after that period of time isn’t really important.
The sensible middle ground (which Apple used to push a lot with the first iPhones, when everyone was complaining about non replaceable batteries) is for the manufacturer to provide a service where they will put a new battery in for you, for the same price that it would cost you to go out and buy a typical manufacturer branded battery (i.e. effectively we’ll do it for you for free for the cost of the part).
I’m not sure if Apple do that anymore. I think now that everyone has got used to the idea of non replaceable batteries, they probably don’t feel the need to be so nice about it anymore.
I must admit that Samsung are making the argument for having the battery not user swappable increasingly weak. Apple will tell you that they can provide a slimmer phone with better battery life by having it built in, but last time I looked the GS3 was pretty damned thin :)
The sun is dying, slowly exhausting its supply of fuel. When you look at it like that, expending the effort in designing and marketing new mobile devices, when in a few billion years life on earth is going to wither and die, just seems futile. :)