Scholarly publications have been hit hard over the past few years by free content on the Web, rising print production and fulfillment costs, and tight academic library budgets. For some the ability to sell subscriptions to online versions can mean the difference between staying alive or going under. Here's a great Case Study that details how Sociological Research Online transitioned to a paid $150 per year electronic subscription model. Even if you're not in scholarly publishing, you may find the technical details of how the journal handles IP authentication useful.
Best quote, "Subscriptions are a necessary evil. In order to maintain the quality and secure the future of the journal some income is required." You can say that again. http://www.firstmonday.dk/issues/issue5_9/peters/index.html