Official figures show students from the rest of the UK (RUK) accepted by Scottish universities have risen by more than 15% since last year, from 4350 to more than 5000.
Numbers from England have risen by 26% and the final figures could be even higher, with several weeks before courses are closed.
Because RUK students now pay average fees of £6800, compared to £1800 last year, the rise will bring an estimated £25 million extra into the sector in the next academic year, rising to more than £100m in four years.
However, as universities receive no public funding to pay for tuition costs for these students, not all the extra money will be classified as profit. And not all universities will benefit equally.
St Andrews University said it had a 9% increase in RUK acceptances this year, with Edinburgh also experiencing an increase, but Glasgow is currently down 20% on 2011, although officials expect numbers to grow.
Other universities such as West of Scotland, Queen Margaret in Edinburgh, and Robert Gordon in Aberdeen traditionally have much smaller numbers of RUK students.
The situation has arisen because, for the first time, there is no limit on the number of RUK students Scots universities can recruit and applications for placings have remained buoyant.
Universities Scotland, which represents university principals, welcomed the overall rise as an endorsement of the fee levels set by institutions and the international renown of Scottish higher education.
Alastair Sim, the organisation's director, said: "Scottish universities had to pitch their offer of fees just right to continue to attract students from across the UK. These figures show students from the rest of the UK have voted with their feet to receive a quality Scottish higher education in greater numbers."
NUS Scotland, which represents students, called on universities to ensure any profits were tempered with generous bursaries to ensure access to university was fair.
Robin Parker, NUS Scotland president, said: "Universities should not be putting profit before academic concerns and, most importantly, must ensure they have bursaries in place to protect the poorest students from the rest of the UK who come here to study."
The figures from the University and College Admissions Service also show there is no truth in suggestions Scots students are being squeezed out of places by their counterparts from England – or the rest of the European Union.
The number of Scottish students accepted so far is nearly 26,000 – just 0.2% down on last year. The number of EU students is almost the same as last year.
Michael Russell, the Education Secretary, contrasted the figures with the situation south of the Border, where university applications are in decline.
He said: "The latest figures show Scottish higher education has remained resilient in the face of significant drops in acceptances elsewhere in the UK following the Westminster Government's decision to charge £9000 fees for all students.
"These figures show Scotland is an increasingly attractive place to undertake a university career."
On Wednesday, the Scottish Government announced a new students support package with more than 100,000 Scots eligible for new loans and a minimum income guarantee of £7000 for the poorest students.