When should the punishment fit the criminal?

My mom links to a news story about a Swiss man who received a fine of $290,000 for speeding. The fine was so high because of his extreme wealth: he supposedly has over $22 million to his name. (He was going 35 miles per hour over the speed limit.)

My mom first defends the fine but then challenges us to think about its implications:

[Y]ou can't punish very effectively with a fine unless you take the individual into account. This guy shouldn't be able to casually buy his way into having the rules not apply to him, which is what it would be if he paid the speeding fine that would burden lesser folk but is nothing to him.

Now, let's extend this idea. Take a guy who loves solitude and spending time at home reading. Some other guy has lots of companions and loves going out every night and working and playing outdoors. They commit the same felony. Should they get the same prison term?

No, the principle justifying a variable fine in a speeding case doesn't extend to the prison hypothetical.

First, it would be too hard to collect accurate evidence of people's personal preferences even if we decided they're relevant in principle. It's relatively easy to determine someone's net worth. I'm not saying the evidence couldn't be fudged, but a court at least has a good chance of determining the answer within the right ballpark. If there's a legal standard having to do with something as amorphous as "how you like to spend your time," it would be practically begging both sides (especially the defendant) to lie.

Second, you'd need to consider that the introverted bibliophile doesn't love anything that can be labeled "solitude." Surely his preference is for comfortable furniture and soothing decor and access to a particular library of books and so on. For that matter, you could say that after all the extrovert's outdoorsy activities and adventures, he would actually benefit more from the solitude of prison than the introvert would; at least it could be said to balance out his earlier experiences.

That's all mostly beside the point, though, since the unpleasantness and unfreedom of prison can be presumed to be equally undesirable to everyone. Money has a fixed, objective value, which accounts for its diminishing utility. That is, the richer you are, the less personal value any fixed amount of money tends to have for you. But the desire for liberty is universal.