Can some types of knowledge be considered "luxuries"? Here's Robertson Davies' take on "ornamental knowledge":
Well, allow me to introduce myself to you as an advocate of Ornamental Knowledge. You like the mind to be a neat machine, equipped to work efficiently, if narrowly, and with no extra bits or useless parts. I like the mind to be a dustbin of scraps of brilliant fabric, odd gems, worthless but fascinating curiosities, tinsel, quaint bits of carving, and a reasonable amount of healthy dirt. Shake the machine and it goes out of order; shake the dustbin and it adjusts itself beautifully to its new position.