As an English speaker, the original makes perfect sense to me and sounds far more natural than your suggested replacement. They’re asking that you not spend mon

As an English speaker, the original makes perfect sense to me and sounds far more natural than your suggested replacement. They’re asking that you not spend money on the book if to do so would impose an undue hardship on you. I also feel compelled to note that “Affording the textbook is necessary to buy it” is itself an incredibly awkward turn of phrase. I wouldn’t normally point this out, but if you’re going to be giving out unsolicited stylistic advice, you may wish to start there.