Do you perfer to photocopy books or buy a book though it is more expensive

When i was studying i do photocopy books that we have to use in our subjects. cause it is much cheaper when it is photocopied and also i don't intend to keep that book in my home. i will just choose which photocopy and which to throw away after using it. cause not all are that useful and worth keeping to reread from time to time. and i don't want to clutter with too many books. also many parts of the book itself we didn't tackled and will not in any way read them in the future. and other parts of the books are not important for me and not that helpful and so ijust choose which part i should have a copy to read .