I do this more as a hobby too. I know some people do this at $1,000 a pop, but honestly, a weekend worth of work is not worth $1,000 for me. I usually work with people who would benefit from having that extra money in their pocket anyway. When you land on something that is THAT good, it's priceless.
And I do this for individuals, not companies. Companies are a PITA to deal with because there's too many people involved. The biggest group I've dealt with was a director, his producers, and a few PR people. And I got that gig because I worked with that producer in the past. Cheap labor has its perks.
Not many web designers get the chance to look at the official guidelines set by a distributor on making a website to promote a movie. They usually have people in-house to do it. They liked my casual communication style, and willingness to listen, and advise on changes as needed, so they refused to use the other guys.
I also have a client who's a hairdresser, and I've done two sites for him too. He travels all over the place and has been featured in magazines, does celebrity hair and all that jazz.
But I've also worked with people who hired me, then decided to get a more expensive redesign later on by someone who just blows them off a month later. So they come back to me looking for help to make quick changes.
And whether it's 3AM, or 5PM, I do those changes then and there.
For me it's more about the experience, and I choose who I want to work with. Obviously a lot of you work on really boring e-commerce websites, and you probably spend hours setting things up. I would never commit myself to do a site like that, unless it was like a fashion store that needed to be pretty and sophisticated, and would benefit from a really chic design. But then I'd rather get free clothes in return.
I would also quickly put together some PDFs showing a client how to fill out the info themselves, that way instead of just writing it all down in e-mail, they can go ahead and have it ready and I don't bore myself to death with it. I want people to be okay with editing their sites afterwards.
And I don't really care about the money. I care about people's crappy online presence and making it look better and being able to say that I was responsible for it. There's too many designers hanging out on Dribbble all day, with high prices, waiting for a bite. I'm not as good as those people of course, but I'm also aware that most of those dream clients of theirs can't afford their prices.
And that is exactly why I stick to $100. It's just extra cash in my pocket anyway.