If they spent a good chunk of it at the time and you don't let them discharge that fine in bankruptcy, isn't that basically a sentence to a life of poverty to pay back the $X million owed? Median US income is about 90k, let's say that left him owing 4M (less than half of 8M + interest), that's 44 years to pay back 4M even if the entirety of your salary was going to it.

Is "forfeit what you've got and go to jail for 18 months" harsher than that? I'd pick the one that let me get a clean start after.

And in the case that it wasn't spent, and by fine you mean as a replacement for any forfeiture, not in addition, then sibling comment has a great point that "if you get caught, you just gotta give it back" is an incentive to commit fraud, not one against committing fraud.