For California, about $250.

http://www.expertlaw.com/forums/showthread.php?t=65923

Good chance the court and DMV will screw things up, such that it could affect you insurance. You will have to jump through some hoops to try and fix it.

You might get the fine reduced or cleared by taking traffic school. I think CA gives it online now.

About the only way to get it completely cleared with no impact to you is; go to court, hope the cop does not show up, and tell the judge that the state has not met their burden of proof.