How much will a speeding ticket cost in butte county California for doing 70mph in a 65mph zone?

It wouldn't happen. Butte county has a policy in place where you can't get a ticket for less than 6 over the speed limit on any road over 45MPH. It's because cars can have too much air in their tires or old equipment, so when the cars speedometer reads "45mph" they're actually doing about 50. Those people are often violating the law by complete accident and ticketing them was considered by the county to be unfair and a waste of government resources. That being said, all speeding tickets 6-25 miles over the speed limit have a $147 fine in Butte County.