I'm a designer and previous developer myself, but the site is actually quite broad. There is a lot more than meets the eye, such as: - an administration area - caching and indexing mechanisms - web scraping robots - various other agents and robots to update user feeds, top lists, etc. - algorithms to calculate relevance and weight for the items on each list - Wordpress plugins, possibility to embed lists, etc. ...and so forth. It's a pretty big site.
If the project was too expensive, blame also the founders , which may have asked for a MVP bigger then the necessary.
The 'additional' requirements that were listed to justify this such as administration area, caching layer, feeds, etc are really basic items.
So unless they wrote their own web server I don't see any issues with flagging this.
For all you know that figure could have been made up.
Just a general observation, I don't know much about your architecture.