It probably is all about economics, but not in the way you think.
The NHS has been importing cheap labour for decades. Doctors with good skills and experience willing to start at the bottom of the pay scale in return for salaries that are higher than in their own countries and with the promise of settlement rights for families.
With no protection for doctors already resident in the UK (Boris' dropping of the Resident Migrant Labour Test used in places like Australia) whether it be those just finishing F2 and doctors from overseas who have come to the end of short term contracts, are struggling to find work. Application numbers for entry level jobs are often in the hundreds and sometimes thousands.
These doctors have no choice but to leave the profession, move abroad or to try to survive on a very limited number of zero hours shifts.
So the NHS continues to import doctors forcing those already in the country to leave.
This obviously will have an impact on salary. DD almost certainly will have to go to Australia. I doubt she has even looked at the salary or cost of living. It is a job, and she needs a job. In the same way as many doctors with a huge oversupply from private medical schools (India and Malaysia are examples) will come to the UK. Doctors starting out on their careers need experience.
This constant importing of cheaper labour is probably having an impact on overall wage rates. I think I read somewhere that over a third of members of the BMA qualified overseas. There is certainly a noticeable lobby in favour of the status quo, perhaps because recruitment agencies, PHAB training etc have been profitable sidelines for UK based doctors. (Interesting to see that BAPIO, yesterday have changed their approach effectively conceding that the problems facing UK graduates need to be considered - I can post the letter if people want.)
Anyways once in the system overseas doctors may feel they are doing more work whilst earning less than colleagues, and without training/promotion opportunities. When application numbers are in the thousands, it can be possible for the NHS Trust to recruit someone with ten years experience and additional qualifications, rather than the newly qualified doctor the job was designed for. Whilst the availability of a cheap supply of doctors from across Asia and Africa means that wages overall are supressed.
Both groups feel wage parity should be restored. The BMA leader Dr Melissa Healy is not from the UK and did not study here. I would be interested in why she chose to study in Italy rather than NZ, and then why she chose to take up a training place in the UK rather than in either NZ or Italy. Perhaps at the time the UK offered better opportunities. But given the way human nature works, she now wants pay parity with other countries, presumably including NZ.
Neither group probably cares much about the many young doctors who don't have work. DD had hoped she might be able to pick up a maternity leave cover, but the department does not have the budget for that cover. Existing doctors will have to stretch further and wait lists, already far too long, will get longer. Existing doctors may then be right to feel they deserve more pay, and won't be thinking that the additional cost will mean even fewer ad hoc opportunities for DD and her peers. Overqualified doctors recruited to entry level jobs won't be thinking that their recruitment deprived UK F2s of a career. Instead they are working hard and above their pay grade so will be feeling exploited.
What is shocking and shameful is that the BMA are doing nothing about doctor unemployment, and the causes. Instead they are using F1 t&c as the basis for their claims, F1s who if things don't change, will probably have to emigrate to find work.