Implementing Frank’s Law would cost about £300 million a year, meaning the total personal care budget would rocket by almost 60%, according to Scottish Government analysis.
In a letter to Holyrood’s public petitions committee, Health Secretary Shona Robison cited the figure from work carried out by her officials and Stirling University’s Professor David Bell.
In 2013-14, the cost of providing free personal care to older people was £494m.
Amanda Kopel, who is campaigning to close the loophole which means people suffering from degenerative diseases have to pay for home care because they are under 65, said she hoped ministers are nearing a solution.
She said: “If they have costed it and had all these extensive talks they must be nearer to saying yes or no. I honestly feel we are just about there. If they turn around and say no, we will go further.
“We have secured a massive victory because who would have even thought about something like Frank’s Law even 20 months ago?
“Now people are coming up to me in the street to speak about it.”
Amanda’s husband Frank, the Dundee United and Manchester United legend, was diagnosed with dementia at only 59 and died shortly after his 65th birthday.
The Kopel family paid thousands of pounds in care costs for him until just weeks before his death because of the loophole.
The Courier has backed Amanda’s campaign, as have a number of footballing legends.
In her letter to MSPs, Ms Robison said she wanted to discuss a variety of options to “improve the fairness of the system”, including raising earnings thresholds so more people become eligible.
The Dundee City East MSP wrote: “(Professor Bell’s) advice was helpful in clarifying what the likely costs may be of extending free personal care to those under 65 and for raising the income threshold at which charges are applied.
“Our estimates include the initial cost of removing charges, and the longer-term costs, factoring in those people who would currently meet eligibility criteria, but currently do not receive local authority-provided care.
“The longer-term costs, factoring in additional demand from those who would be eligible, are more difficult to accurately forecast but must be taken into account in the light of our experience of growth of demand in the roll-out of Free Personal and Nursing Care since 2002.”