You're absolutely right. The graph could have been clearer, but I should have double-checked my assumptions and that $.30 per resident figure should have been a red flag. I apologize for that basic error.

Looking into this more, it sounds like, while there probably is a perverse incentive because more tickets equals a significant increase in revenue, the biggest problem is the punitive fines for minor non-traffic offenses that tend to compound for poorer residents: https://www.motherjones.com/crime-justice/2018/02/how-does-c.... Note the headline is a little misleading, they seem to mean "non-moving violations".