I guess there are some edge cases. Drug smugglers for example are probably aware of the rough probability of detection and weigh it up against the length of jail time. But I reckon Sarkozy thought he'd just get away with it and didn't even consider what the potential punishment would be.
It's worth considering then that the next person who has the option to do this might behave differently, given Sarkozy has not got away with it.
You're implying that imprisonment makes people offend more - perhaps the simpler explanation is that most criminals will commit crimes when they get the chance, especially prolific criminals. Prison takes them off the streets and stops them victimising more people - this is helpful.
* An honest acknowledgement of ones behaviour and its impact on others.
* Accepting the consequences of your behaviour, whether legal (such as going to jail), financial, or personal.
* Taking the initiative to make amends where possible.
* Taking steps to improve oneself and/or prevent the same behaviour in future.
For a nuanced discussion, the Illustrated Guide to the Law is an excellent introduction. Here's the section on Punishment: https://lawcomic.net/guide/?p=41
It ends with the summary "The State punishes those who commit crimes partly in the hope of preventing future offenses (via rehabilitation, deterrence, and removal)... partly to restore a sense of balance and fairness (via retribution)... and partly because fuck you, that’s why (retaliation)"