Starter cactus farm

A four cactus starter farm by SurvivorCraftX, 38 seconds long and eleven blocks in total. Four cacti on sand with three fences between them, water washing the breaks into one hopper and a double chest. There is nothing clever in it and nothing claimed for it, which is the point: it is the cheapest thing that will produce cactus at all, buildable the hour you find a desert, and it stacks upward if you later want more.

It stacks. Pizza_61 points out you can add as many layers as you want, which is the only way to get a meaningful amount out of it.
raymondstheawesome writes the fair summary and nobody argues: on material cost, build time and simplicity it is excellent, the rates are poor, and the creator never exaggerated anything.