Fake likes come from click farms, these are located in countries such as Bangladesh and India. There people are paid with few money to sit and log in and out of different Facebook accounts and give likes to a number of pages. The fact that 2000 likes cost $4 is explained through the idea that those click farmers receive about 1 cent for a like so there you have the explanation for "why so cheap". If you ever have the curiosity you can check the profiles of those who "liked" a certain page, they either have no photo, or no relevant information about them and they don't have any posts or shares of their own. Facebook bans likes received from bots so it created its own ad business by charging you as much as $5 or more, but the thing is this works also on click farms. So, the best likes are those you gain organically from devoted fans.
