Fair enough, costs are quite high when talking about DND airport and students don't like high prices (I know, I was one in Dundee for 4 years and used the airport once to come back from BHD-£76 single booked 4 weeks in advance)!
However, the cost of getting down to EDI or up to ABZ from Dundee does add up. The cheapest way to EDI is a through megabus ticket, which although good value, realistically rules out any flights before 11:30am (earliest arrival time at EDI is 0955) and any flights that arrive after 7pm (latest departure from EDI is 1925). Before the first bus time it's an expensive train and bus or taxi journey and after that time it gets awkward with buses etc. I know, I did it many a time!
I know DND will never rival the likes of LHR or probably even INV, but perhaps if a few more regional routes were started up then overall costs could become low enough for the services to attract the punters in greater numbers!