It seems like it would cost around 2k for the hardware to make a complete mirror of this library (31TB for this library, and similar again for Lib Genesis). It's a lot, but considering what used to be spent on the beautiful buildings to host major libraries, it's something that is within the reach of a very large number of people.

It does require being OK to fall foul of copyright law in most countries though, which I expect keeps a much larger number of people away.