This is not necessarily true. There are people who spend more on a seedbox or VPN each month than a Netflix + Rdio/Spotify subscription cost.
Furthermore, private trackers have restrictions on them (ratio limits, etc.). Depending on what kind of content you're looking for, it's not exactly "free" either in money or time to be an active Bittorrent user.
It just so happens that that cost is still less than the "legal" alternative - if a legal alternative even exists (look at pippy's comment about accessing content in New Zealand).