Emergency physicians covering vacancies at WA public hospitals in country areas are being paid $3500 a weekday and $3900 a day at weekends and public holidays.
And some doctors pushed to be paid $5000 a day during negotiations with the WA Country Health Service last year, but the Government refused.
The Australian Medical Association WA said the lucrative daily rates, which did not include superannuation, were "appropriate" and reflected many years of training.
Health Minister Kim Hames said the pay rates were one of the reasons WA's public hospitals were more expensive to run than those in other States.
The daily rates are paid for 24 hours of medical cover by an emergency physician locum, who is expected to work a 10 to 12-hour shift in an emergency ward during the day and be on call at all times overnight.
Dr Hames said Kalgoorlie Health Campus had been the biggest user of fly-in, fly-out emergency locums, but the WA Country Health Service refused to provide details about how extensive the practice was so as not to identify individual doctors.
"The WACHS rates for emergency physicians, who are Fellows of the College of Emergency Medicine, are a maximum of $3500 for a weekday and $3900 maximum for weekends and public holidays," Dr Hames said.
"These rates are for emergency physician locums, and generally only when continuity of service is at risk.
"WACHS continues to work towards more salaried workforce arrangements wherever possible, and more locums on the standard locum day rates."
Dr Hames said Kalgoorlie had recently appointed a head of emergency medicine and a second emergency physician would be employed soon.
Shadow health minister Roger Cook said the costs reflected the difficulty of attracting doctors to the bush. If the Government had an "adequate workforce development strategy", it would not have to use as many FIFO doctors "at these exorbitant rates".
"Dr Hames needs to engage more actively in his portfolio and come up with a better plan for the health workforce," Mr Cook said.
"Where possible, we need to employ salaried physicians to reduce costs to taxpayers. This means the Government must do more to attract local medical graduates to take up posts in regional WA."
An AMA spokesman said the payments "also represented time away from families and general dislocation to lives that specialised emergency locums were willing to tolerate to ensure that the health needs of rural West Australians were properly met".