I would think it should be in a region of over £100k in the uk.
it depends if they are working as a doctor or driving cab
Amazingly little. Ph.ds rarely make significantly more than people with masters degrees. I have an MBA and my husband has a Ph.d, and I've often made more than he does. Having a Ph.d puts you into a niche that's hard to get out of, and people who get one usually want to either teach or do research. They normally get one for their own self-gratification... not the money. Paying back the school loans is usually NOT worth the effort unless you have something specific in mind that you want to do something that requires one.
A very broad range of incomes...a veterinarian may make less than $100K,
a college professor $150 - $250K. A general practice country doctor $150 - $300K
a surgeon $300 - over a million. A published surgeon that has invented life saving devices $1 -$? millions...
It's not like a government pay grade. The answer requires some clue as to what the PhD is in, and what exactly are they doing with the degree...?
You can have a PhD in Nosehair Weaving of Prehistoric Indonesia. You still will only be making about 10-15% tips at the diner serving tables, despite being the premiere expert in your field.
Public health... not so much, unless it is the color of the administration job, so to speak. Microbiology... well, depends on WHO you work for. If you do go microbiology, please do some research-- a TON of microbiologists have been turning up dead lately of mysterious circumstances. It's got the conspiracy dudes in an uproar.
if it's a liberal arts phD, he's probably unemployed or making minimum wage