Most things do, which is good news. I'd be interested to know if there are any projections of how these costs may be reduced. Do you have any references on hand?
4chan is a big place with a long history. It's kind of like 50 different websites and communities under one domain, where there's surprisingly little overlap between them all. I think you'd find that most people who visit the less notorious boards on 4chan are your totally normal geek crowd.
Yep, Prolog is pretty great for that kind of thing. I'm working on a project right now where I'm using Prolog (via tau-prolog) in the browser to determine permissible input options based on the user's existing selections. I'm also using it (via https://github.com/mndrix/golog) to apply those restrictions on the server, and to calculate the pricing for a configuration. In most cases I'm generating Prolog code from a collection of tick boxes, but for complex campaigns I can dig in and write a specific implementation of the required rules. Very flexible.