What is the difference between an international textbook version and a regular one?

I need a textbook but the original version found in my college costs over $130 but online I can get one for $70-90 but it's the international version does anyone know the difference?What is the difference between an international textbook version and a regular one?
i acutually had this happen today.i contacted the seller and they told me that the only difference is the page numbers and the look of the book (i.e. cover may be paperback, and the picture on the book). its the same material except it was printed in another country but is still in english.

i've also read some other fourms and post and they said its really worth it, its just a cheaper quality of paper and very cheap. i listed the website in the source box for you.