MINNEAPOLIS -- It's no secret that college is expensive and a contributing factor is the price of textbooks.

According to Student Public Interest Research Groups, the cost of a college textbook increased by 73 percent between 2006 and 2016.

"The Deal Guy" Matt Granite says students and parents can use CampusBooks.com to compare textbook prices.

Granite also recommends a free 6-month trial of Amazon Prime Student. While Amazon's website advertises a savings of up to 90 percent on textbooks, Granite says in his experience it's usually 40-70 percent but he still calls it a "substantial savings."

Related: How to lower your textbook costs up to 70%

Meanwhile, some professors are saving students even more money by using open textbooks -- made available for free online.

"The Open Textbook Library started at the College of Education and Human Development here at the University of Minnesota five years ago and now has 400 books and over 1,000 faculty reviews of those books in disciplines all across the curriculum," said Sarah Cohen, managing director of the Open Textbook Network.

According to Cohen, about 600 campuses across the country are a part of the Open Textbook Network.

"Those books are available to faculty anywhere around the world and so those books are available online for free. The books can be downloaded directly onto your computer, they can be printed because they have a license that allows us to print, and they can be used online. So there are options for faculty and students to use the books," Cohen said.

Starting Monday night, about 100 representatives from campuses across the country will be at the University of Minnesota. They will spend the week learning new ways to build open textbook programs at their campuses.