In a sense, it's the replacement that someone who has their bike stolen is paying for, not the original. If it gets stolen, you'd need to get a ride home, find a new bike without transportation for a bit, and put in a decent amount of time and money to fix a bicycle at that price.
The bike cost $30. If I get one stolen every 10 years, I figure I'm paying $3 / year for the convenience of not having to bother with locking or carrying a key.