filtered water

me : Why the waste of money on textbook?

him : Study, doh!

me : Textbooks are like unfiltered water, it contain a lot of minerals and even more impurities, this is why textbooks have a lot of useless information inside.
me : Where notes are like filtered water, it only contain minerals and no impurities, everything you need is inside. This is why I never buy textbooks.

him : But the notes are useless.

me : That is because the filtered is too damn good. It even filtered out some of the minerals.

Money spent on me is money well spent. money spent on textbooks is not.