This sign states that the fine for illegal dumping can range from $600 to $12,500. An older version of the sign, visible on the reverse side, dates from a time when the upper limit was a mere $1,500. I don't know when that was, but I did find an NY Times article that says the maximum fine was raised from $2,500 to $12,500 on January 1, 1985.
Now even the newer sign is out of date. The current range of fines for illegal dumping is $1,500 to $20,000.