For the company I work for we build websites in the 100k - 500k range. Our first clients came from a professional relationship my boss had before he started the company. Then gradually as the company did work we gained a reputation for the sector, and in the products of our core compentencies. Now we have more leads then developers to finish them. They come from referrals of other clients (everyone in the sector seems to talk to each other) and a large part comes from our business partners (the companies that built our web platforms) referring us.
This is exactly where we want to end up. It's all about building reputation, you and a couple of others have pointed out that word-of-mouth is by far the most effective way of gaining this. For initial clients, we are just going to have to continue promotion in our own professional network.
