Most people could cheap out on tools and they'd still last. The average person just doesn't use the ones they own very often or work them particularly hard. Really, you're going to know if your usage will require higher quality tools and it's not the average techbro posting on /r/buyitforlife.
Backpacks are similar. If you're just using one lightly loaded for an urban commute there is nothing wrong with cheaping out. Spending more is really for people who are wearing them hard and filling them to capacity.