No, we weigh the cost of prosecuting a specific crime against the cost of not prosecuting it, and let some crimes slide.
So we spend a lot more time and effort prosecuting a murder than a jaywalker. Because it's worth more to stop the murderer.
(And when this gets out of whack, we have problems. Red light cameras, GPS devices on cars, and such are reducing the cost of prosecuting some crimes, and that is causing social problems as we start to prosecute crimes that we didn't before. A lot of the complaints about the TSA is that they don't care about the cost: They just purse to the hilt. And the NSA has the problem that they only count the direct monetary cost, not the social, diplomatic, or economic costs.)