Everytime I see someone trying to put down high earners by saying "I work just has hard/even harder than you, I could do what you do"... I think, well... Why don't you?
THAT is the big difference.
Lower paid jobs are easier to get. The job itself may be hard, but the opportunity is significantly easier.
Higher paid jobs are harder to get. The actual job itself could be easy as pie, but the steps to get there (qualifications, promotions, travel, timings, risks etc) are a lot harder.
People often use Nurses as the low-paid, hard-worker example.
But up until very recently, one could take a Nursing degree for free (and the entry qualifications were quite low) and then get a job as a Nurse very quickly, as its an in-demand role. It also has a distinct pays ale, so you are guaranteed a certain income which steadily increases along with your experience.
A lot of high earning jobs have a far less linear entry path, far fewer job opportunities and are more competitive to get into.
When it comes to being highly paid, the hard work isn't restricted to just what the day-to-day tasks are.