I also agree that once the sentence has been served, people should not be punished any further, except where the occupation requires a clean record. e.g. I would be OK with pharmacies requiring no arrest for drugs etc. as a condition for employment, or drivers without DWI convictions etc.
I guess my point is: its not a purely economic decision. Sure you're losing tax revenue, but that's because you're:
1) Protecting society from a person who has demonstrates some lack of understanding/acceptance of its rules.
2) Cause significant discomfort/pain to the perpetrator of the crime so that they realize the consequences of breaking the law and hopefully never do it again.
On the other hand when someone boldly ignored certain moral rules, will the person continue to do so? I think it's pretty serious when someone else had to suffer because of that.