Not necessarily, the fine just needs to be a sufficient size.
Fines are not assessed that way.

Some are, but they often have maximum caps.

So for a UK speeding fine he’d get a £1000, but if it’s wasn’t capped it would be somewhere in the region of 340 million.

Your Speeding Offence Details

Speed Limit: 30 mph Recorded Speed: 35 mph Excess Speed: 5 mph Offence Band: A Road Type: Standard Road What This Means For You

Your offence falls into Band A, which carries a fine of 50% of your weekly income. Based on your weekly income of £640,000,000, your calculated fine is £320,000,000. This has been capped at the maximum of £1000 for standard road offences.

Why would any such fines be capped, unless the entire point is to effectively legalise crime for the ultra rich?
You sound surprised?
More chagrined than anything else. Having dual citizenship with US and UK is like having one foot in the grave and another foot in the toilet sometimes.