1) The stack is Rails and Postgres on Heroku, static assets (video/images) on S3/Cloudfront, and transloadit for video processing. $2500 isn't a crazy sum but the project doesn't make any money and the value for us is mostly the fact we created the website. Like any public project, the other non-intuitive costs are maintenance and customer support. We love that it's become a resource so we're moving everything to a static site and keeping the work archived.
The new beta is focused on B2B (with a need) and a lot of the manual processes of uploading and formatting projects has been automated, which is how we can offer the "human" element.
2) We had zero spend on advertising since the content is so damn compelling. A couple of projects hit the top of reddit/fb/HN.
3) The "main" project is our digital consultancy in SF which a small part came as a result of Monograph exposure. The business is growing, but we really enjoy building products so the beta is a primary focus for us this year.