It's one of those "80/20" things. You can get 80% of the technology for 20% of the price. Just look at the price of 3GHz compared with 2GHz computers. The price/spec curve is linear until it gets to the stuff that wasn't around a year ago, then the price goes up like a Yak on steroids.
You probably don't *need* this Formula 1 winning performance for most of what ordinary folks do, so buy something that's about a year old tech, and you'll find you can get a pretty good box for £700 or so. Monitor is extra - CRT ones are now very cheap, the ones with flat panel LCD are expensive. If you've got room for a CRT one...
DVD writers do CD writing and reading. But do you *need* to write DVDs? I find I can get all the stuff I need onto the occasional CD.
I built a "state of the art" machine about four years ago (at considerable expense). It's now a museum piece, but it still does all the things it did then, and it's more than adequate for my needs.
What you will need is USB (for the digital camera and the ADSL modem and maybe the printer).
Printers - inkjet (or bubblejet) are fine. Best to get the ones with three separate colour ink cartridges cos that way you don't waste half the ink in the thing. Printers are cheap, ink absurdly expensive.
Laser is excellent if B&W will do - quality's sharper, and damp doesn't make the print go foggy. I've got both, laser for serious stuff, bubblejet for colour pix and stuff.
Now software - that's a whole new ballgame. There is freeware stuff out there that does almost everything Mr Gates's bloatware does. If you have ADSL, you can download it and try it in profusion.