What cognitive bias does this reasoning exhibit?

I just saw ad advertisement for a chemistry textbook I need next semester. They had three options: $$59$ for e$-$book only, $$125$ for hardcopy only, and $$125$ for e$-$book and hardcopy. I$$m definitely going for the $$125$ e$-$book and hardcopy, even though I really only need the e$-$book. It$$s such a good deal comparatively, I can$$t turn it down