Actually, the sell-for-half-price rule is in the Equipment section of the 2014 rules.
Selling Treasure
Opportunities abound to find treasure, equipment, weapons, armor, and more in the dungeons you explore. Normally, you can sell your treasures and trinkets when you return to a town or other settlement, provided that you can find buyers and merchants interested in your loot.
Arms, Armor, and Other Equipment. As a general rule, undamaged weapons, armor, and other equipment fetch half their cost when sold in a market. Weapons and armor used by monsters are rarely in good enough condition to sell.
Magic Items. Selling magic items is problematic. Finding someone to buy a potion or a scroll isn’t too hard, but other items are out of the realm of most but the wealthiest nobles. Likewise, aside from a few common magic items, you won’t normally come across magic items or spells to purchase. The value of magic is far beyond simple gold and should always be treated as such.
There doesn't appear to be an equivalent entry in the 2024 rules.
In any case, unless the party has a lot of downtime, making enough excess potions to sell is generally going to be pretty rare, and not worth worrying about. Also, for druids, the
goodberry spell already allows them to hand out healing items to the party and not worry about casting spells in the heat of combat.