NHS Ayrshire and Arran has spent £433,000 in the nine months to the end of December last year -or £48,111 a month - in salaries for 11 different locums for Cumbrae.
The island's previous GPs quit last April after a long-running battle to prevent a community pharmacy from opening, leaving the health board to use locums to provide round-the-clock medical care for some 1400 patients.
Despite three previous recruitment drives, NHS Ayrshire and Arran has struggled to find a permanent replacement for husband-and-wife team Drs Jim and Elizabeth Bryson, who had served the community for 27 years.
The couple took early retirement after they were forced to close the practice's drug dispensary following the opening of a pharmacy in Millport. GPs are only allowed to dispense, as well as prescribe, drugs in communities where there is no pharmacy available. A third GP they employed also quit.
At the time the practice cost the NHS around £250,000-a-year, with the additional income from the dispensary used to cover the cost of the third GP, out-of-hours care and home visits.
Critics said it had also been used to top up the GPs' own incomes, but the case is one of a number that has led the Scottish Government to consider overhauling the rules to bar pharmacies from opening in certain areas.
The board hopes to resolve the situation in the coming weeks with three doctors who have submitted business plans to take over the Cumbrae Medical Practice in Millport being interviewed on Friday.
Jean Kerr, chairwoman of the Cumbrae Elderly Forum, said she hopes the latest round of interviews will bring the saga to a close.
She said: "The whole thing has been ludicrous, and all brought about by forcing a pharmacy on us. An ideal scenario is that we get two doctors willing to stay on the island so that we can have someone around full-time but I don't know how likely that is. But the status quo is no use either."
NHS Ayrshire and Arran advertised the £338,500 practice contract in Millport for the fourth time in less than 12 months shortly before Christmas.
It received seven applications, with three candidates going on to submit business plans - the highest level of interest to date. However, previous recruitment drives have collapsed because applicants could not agree on a salary.
Dr Andrew Buist, deputy chairman of BMA's Scottish GP Committee, said the cost of running rural practices was offputting to applicants. He said: "A lot of these practices might have very small patients lists of around 1300, which is less than a single mainland GP might have.
"When the Scottish Government is only paying you £70 per patient annually, that doesn't leave much to cover overtime, out-of-hours care, extra staff, bills and so on.
"It's a lot of work if you're the only GP, and these aren't high-earning practices. If you want to earn a high income, you'd go to city practices. So you need the kind of top-up funds that come from a dispensary to make it worthwhile."
Local MSP Kenneth Gibson said: "Servicing the health needs of Cumbrae, which has a high proportion of vulnerable, elderly people, by locum for any length of time is expensive and patients cannot get to know and build trust in doctors that change frequently.
"It will be a great relief for islanders to have their own island based GP service re-established."
Dr Alison Graham, medical director at NHS Ayrshire and Arran, said: "Patient safety is always our first priority. NHS Ayrshire & Arran has a duty to ensure there are arrangements in place to provide safe, effective and equitable care for everyone in Ayrshire and Arran.
"Since April 2013, we have employed one full-time locum GP on Cumbrae to ensure continuity of care for the local population. This has been supplemented by a further seven sessions to ensure sufficient cover. These additional sessions have, in the main, been covered by two locum GPs, again to ensure continuity of care. The remaining locums have been used mainly to cover shifts during leave or when the three main locums have not been available.
"We will continue to use locum GPs on Cumbrae to maintain a safe level of service until the practice contract is agreed."