There are some online schools that offer free virtual curriculum (cost inclusive in the fee) but several of them require students to source their reading material and textbooks from outside. Thus, like regular students, online students too end up spending a fortune on buying books.
However, with the availability of free books online, there is definitely a way to save. There is increasing awareness of free downloadable textbooks available on the Internet on almost all subjects. Most of these books are old classics. All you need to do is to find the correct resource and use it effectively.