Well said, Frahse. I actually took it a step further and developed my own CMS system because I didn't like any of the existing content managers out there. But then again, I do development for a living (among other things) so that's sort of a given. But even if you can't do basic HTML, there are lots of great free sites out there that will get you on your way. One of the generally panned, yet still effective ways to do this is with a blog site. I know a number of authors whose only website is a blog on a public blogging site such as Blogger or something similar. Yeah, it's not much, and might be a little amateurish, but it gets you started. Plus, if you're short on cash, it's a good way to get started as they tend to be free.
Now, for more professionally designed sites, these can range from a few hundred, to something in the five digit category, depending on the developer and the type of site you want. I'd say in general, at least for a professionally designed author website, anything between $600 and $3000 is about right. Above $3000 they're taking you to the cleaners, because a site like that ought to be one step short of a 4 star hotel when it comes to websites. Below $600, unless they're doing you a real favor, is typically either bad quality, or insulting to the developer. (they have to pay the bills too) But anyways, that's my 2c on what to expect on that side of things, which is coming from a guy who does them for a living, so I've pretty much seen it all.