Clearing - the process in which students without university offers compete for unfilled places - begins next week after A-level results are published on Thursday.
Experts say the next few weeks will provide the final test of the effect on applications of the introduction of pounds 1,000-a-year fees. Sixteen per cent of university places are filled through clearing.
So far, there has been no fall in the number of 18-year-olds applying, though applications from mature students have dropped sharply.
But John Dunford, incoming general secretary of the Secondary Heads Association, said universities which accepted students with lower A-level grades from the clearing process might find applicants withdrawing.
Such students might decide that less prestigious universities were not necessarily a passport to employment and a good salary.
He added: "Students who don't get the A-level results they need for the course they want will be more inclined to withdraw. It is one thing to decide to fill in an application form the best part of a year in advance of going to university, and altogether another to decide between taking a job and going to a university you haven't chosen."
Tony Higgins, chief executive of the Universities and Colleges Admissions Service (Ucas) which runs clearing, refused to speculate on what would happen, but he accepted there was anecdotal evidence that some people had put in applications as a back-up and intended to take their final decision after the results.
A spokeswoman for the National Union of Students said: "Students take a risk in clearing as it is. The decision about whether to go into the clearing process becomes much more serious if they are going to have to pay pounds 1,000."
About 20,000 university applicants usually withdraw at the clearing stage. Professor Frank Gould, vice-chancellor of the University of East London, predicted that the number would increase this year because of tuition fees. "But the numbers will not be great. And they will come back in future years once they realise that higher education is a good investment."
Figures from Ucas suggest that students are becoming increasingly cost- conscious. Applications for traditional academic subjects such as the physical sciences are down and those for more vocational courses such as computer science, marketing and business are booming.
The trend is away from the caring professions - such as nursing, social work and teaching - and towards professions which offer better financial rewards.
Dr Higgins said that the number of courses offered by universities created since 1992, which tended to offer more vocational courses,would exceed those offered by the old universities for the first time from autumn next year.