It's not a business transaction, you aren't paying for the opportunity to go too fast, it's meant to be a deterrent. As such scaling with income makes sense, it's only a deterrent if it affects you, and realistically people with lots of money aren't going to be deterred by a relatively (to their income) fine that's going to deter people who are less well off.

How come wealthy people don't drive at 200mph at all times then?

In some places, tickets are strikes on your license. So even if you can afford to pay the measly $500 fine, you can only do so maybe twice. Your third time in two years (or whatever your laws are) will cause your license to be suspended.

This is effectively the system in the UK. You get "points" on your license, at a set number of points you lose your license and can't drive legally.

come to southern germany and see how your premise is wrong. they absolutely are.

what's the incentive not to speed if it only costs less than 1% of your income/net worth?

the risk to everyone else around you is the same regardless of how much you make

Because you don't want to endanger yourself, others, or talk to a cop for a half hour?

This is worse than any financial penalty, even to me, and I ain't rich.

People don't typucally drive at speeds they think are unsafe. When someone is speeding, they generally believe that they are capable of safely operating their vehicle on that stretch of road under the current conditions.

Avoiding the time wasted while pulled over does sound like a reason not to speed but even there it's a tradeoff. How much time do I save off my commute vs how long a stop would take weighted by the probability of being pulled over.