I have no idea how much it would cost. Facebook started as a very small platform. I don't think you'd need a lot of money to achieve something like that. Honestly, I think that's the future. We can't depend on those big corporations. However, that doesn't mean SJWs and big brother won't try to deplatform you. Countries like the USA, Australia and Canada are known for tracking down and deleting sites that disagree with their political stance. Big states such as those three represent a huge threat to liberty. In other words, even if it doesn't cost a lot to make the web site you'll still need a shitload of cash to keep the lawsuits off your back. Just look at what happened to the founders of piratebay and wikileaks.
