Are there any ongoing costs associated with self-managed web site content?
If you choose the Macromedia Contribute method, then no… there are no ongoing costs (apart from web/domain hosting) in updating your site. Macromedia may, from time to time, update their software, but the decision is up to you regarding whether you upgrade your software or not. If you choose the ‘Content Management System’ method, then most probably there will be ongoing costs associated with managing your own content, depending on the provider.