Why are computers with retina displays so expensive?
Because they use cutting-edge screen technology.
Should you buy one - that's up to you. In your description of what you intend to use the machine for, I think that it would suite you: but I also think that a non-Retina 13" MBP would suit you very well. The 13" gives you more portability, howver, so if that's something that you value, you may want to pop into your local Apple Store and heft both to see which design you prefer. As more and more companies release Retina-ready apps, it's likely that you'll be blown away by the display - and the portability (if that's one of your critera).
I'm still waiting on (at least) the 3rd generation of Retina display MBPs before I'll even consider a purchase. I'm quite happy, right now, with my MBP purchased in March of 2012. Just no problems at all.
Thank you very much! I think I will wait a year or 2, because I like the thin design, but I don't like the price. I love the retina display. I think in 2 years it will be for at most 1499 usd and thats OK, because a non-retina with 128 ssd and 8GB RAM is 1499. And I read Apple are going cut the non-retina this summer. I wonder why the iPad with Retina came out and no price up? I think I agree with you, wait 1-2 years and the integrated graphics are going to be better. They should give it GT3 graphics when Haswell comes out. Thank you for your reply! Have a nice day!