Students from Northern Ireland who go to Scotland for their degree face an average annual fee of just under £7,000 a year.
The University of the Highlands and Islands became the final university in Scotland to announce its proposed fees for students from England, Wales and Northern Ireland.
It plans to charge students £7,500 a year for the first three years of their course, with the fourth year free, giving a bill of £22,500.
All Scottish universities have announced their proposed fee levels for students from the rest of the UK, averaging some £6,841 a year.
A number of universities, including Edinburgh and St Andrews, plan to charge students from England, Wales and Northern Ireland £9,000 from next autumn.
Robin Parker, president of NUS Scotland, said it was "shameful" that Scotland would be the most expensive place in Britain for these people to study in.
Mr Parker said: "When you look at the fact that over 40% of students from England, Wales and Northern Ireland study at Edinburgh and St Andrews universities, where degrees will cost £36,000, the real average degree will cost over £30,000.
"It's shameful that Scotland will be the most expensive place to study in the whole of the UK for students from England, Wales and Northern Ireland. This system is one that simply allows principals to cash in on students from the rest of UK, and that's unjustifiable."