It depends on what the law is for. For example you could have a nice solid fine for littering, with half of it earmarked for public cleaning/improvement. If someone violates that and reliably pays the cost, it's win-win. They get to be lazy and the environment is improved.
Since littering means degrading the appearance of a public space for some amount of time, it's hard yo put a price on it: the maximum fine should be the cost of a person assigned exclusively to you, who immediately picks up whatever you throw to the ground and nicely dispose of it in the appropriate way.
What you say would make sense in case of unpaid fares. In the case of speeding, there is no amount of money that can offset the increased risk to pedestrians and other cars.
No amount? I disagree. The speed limit is inherently a balance between safety and time-efficiency. You can convert time-efficiency into money, and figure out a monetary cost of different speeds. Even if it's an absolute mandate to keep safety levels the same, you could cut everyone else's speed by 1kph and make it up to them with a share of the money. Or you could subsidize safer cars with the money.
And at a certain price point you can call in a police escort or start installing express lanes.
