Note to self

[pozorvlak]

Suppose you have a choice between buying Item A, which is has quality 100 and costs £100, and Item B, which has quality 80 but costs only £50. Now suppose that you are buying these for Application C, which demands quality of at least 90. If you buy Item B, you have not saved £50 for a marginal reduction in quality; instead, you have completely wasted £50.

I keep making this mistake; hopefully now I've written it down I'll make it less often.