> Isn't fairness in law defined as being blind to the perpetrator?

Fairness in this case would mean giving equal fines for equal crimes.

But equality in which units? There's a case to be made that dollars are an implementation detail and that the political system cares about utility units.

If you want the fine to equally disadvantage all parties in utility units then the dollar values are going to be different. Because the idea is that each criminal should be equally unhappy with receiving the fine.