Comment by jiveturkey

It'd be ten times that cost, easily. You have to buy data volume.

Also since you aren't targetting specific people, rather specific interests, it'd be easier to setup an irresistible site serving content of the vice of interest. It can even be a thin wrapper on existing sites. Do you only need to control entry nodes in that case? You'll return user-identifying data in headers or steganographically encoded in images and since you control the entry node you can decrypt it. It doesn't work for a normal (unaffiliated) entry node but since your entry node is in collusion with the server I think this works.