Grass Seeds

For the job they are named after, these stop mattering the moment you find a Staff of Regrowth. It spreads grass for free and never runs out, so buying seeds after that point is money burned.

What keeps a stack in the chest is crafting. They feed a couple of wall recipes and the Biome Sight Potion, and the rubblemaker turns them into small decorative plants, so a few dozen are worth holding even when your world is already green.

The Dryad will not sell them while a Blood Moon is running, which only bites if you were counting on a late night shopping trip.