Yeah...you know, the OP only needs 4GB RAM if he upgrades every two years for sure. But, actually, he really doesn't need a MBP at all for what he says he does. Really, he should get a base model Air, or some $400 laptop.
That's the thing, and why I would argue that it's potentially "worth" getting 8GB or 16GB of RAM for a RMBP. It's an expensive, relatively powerful computer. People _use_ old computers, and it has definitely been my experience that more RAM helps old computers run newer operating systems and applications. Now, that trend might not continue (as a lot of people have argued), but it's hard to know how OSX.12 (especially, say, with a vm running some future version of Windows) might utilize RAM, along with whatever applications people are going to use in a few years. As far as 4GB, there are interesting tests like this one:
http://www.tomshardware.com/reviews/ssd-ram-endurance,3475.html
Again, not an issue for short-term use. But one reason that there are all of these RAM-argument threads is that your mileage may vary, and no one really knows how much RAM you will want in a few years.
That is what is so obnoxious about non-upgradeable computers--it's ridiculous that we have to decide now. But if you'd like your computer's non-recyclable parts to stay out of a landfill for longer (laptops, phones, etc. have a relatively heavy environmental impact--they use rare-earth minerals, and RMBPs are especially hard to recycle:
http://www.wired.com/opinion/2012/10/apple-and-epeat-greenwashing/) you might want to buy a computer that someone (even if it's not you) will still be using in six years or more. When you're done with it, sell it, give it to your nephew, donate it to some organization that needs it. I think that's why the 4GB option is bad; it speaks to having a disposable device.
