Like anything, it started innocently... first a whetstone here and there, then a nickel or dime, not much, but before you know it, they needed kilos of everyone else’s stones.
Whetstones are a gateway. Next comes ceramic rods, then Spyderco ceramic stones.
Then diamond plates. Cheap ones from Harbor Freight at first, then DMTs, then Atomas, from Japan.
Japan! Japan! Japanese water stones, in endless variety, with all the water storage tanks, and other paraphernalia. By that point, sharpening is an end in its self, because the whetstoner has lost all interest in everything else, and never finds time to actually use the knives, chisels, hand plane blades, and straight razors, that have been so lovingly honed to hair splitting perfection.