The price of textbooks for college students has increased by 1,041% since 1977. Flickr / Sewanee College affordability has recently become the preeminent issue in higher education, as student-debt figures have hit staggering levels.

But most conversations center on ballooning tuition costs, rather than a less well-known expense that strains the wallets of college students: textbooks.

Since 1977, the price of college textbooks has more than tripled the rate of inflation, meaning a 1,041% rise, according to NBC News, which cites Bureau of Labor Statistics Data.

"They've been able to keep raising prices because students are 'captive consumers.' They have to buy whatever books they're assigned," Nicole Allen, a spokeswoman for the Scholarly Publishing and Academic Resources Coalition, told NBC.

Some publishers contest the idea that textbook prices have risen exorbitantly, claiming that what may look like stark increases in percentages actually represent more modest increases in whole dollars.

lifesupercharger / Flickr Still, students and experts following the trend say that the prices are becoming prohibitively expensive.

And the high prices are beginning to discourage some students from purchasing textbooks for their classes, despite the fact that they realize it may hurt their grades.

The US Public Interest Research Group (US PIRG) conducted a survey of 156 different college campuses across 33 states and found that 65% of students decided against buying a book required for class due to its high cost. And 94% of those students acknowledged that they were afraid that the move would hurt their grade.

"The textbooks market is broken and students are paying the price," Ethan Senack, a higher-education associate at US PIRG, told US News & World Report in 2014.

"[Students] can't shop around and find the most affordable option, meaning there's no consumer control on the market," Senack said.

They can, however, mitigate the rising cost of textbooks by looking for alternatives, such as buying used books and selling their books after the course has come to an end.