Who the "crown, local lord, and guild" might be will change according to the lands the PCs are in. What follows is human-centric, but one can (and should) imagine a Fey lord will want something completely different as would a Death Knight or Ghoul Guilds.
Players might raise objections to a lot of the below and want a better arrangement. That's absolutely fine and expected. Remember (1) In accordance with GP = XP, they will receive XP for "gross" treasure recovered (pre-tax); (2) only the value they receive in GP is taxed; (3) If they want a better deal they should argue using the in-game fiction.
WHAT IS VALUABLE?
Flora & Fauna
Biles from animals
Nectars from plants
Salts from minerals
Material
Art/Iconography
Books
Rare Raw Goods
Gems & Jewelry
Gems- raw, imperfect, perfect, cut; type associated with a metaphysical/mythic property
Jewelry- magical individual pieces or sets that project power/honor an event
Candleholders, cups, silverware, china- denotes status
WHO WANTS IT?
Professional organizations will want raw materials to manufacture various goods. Biles, Nectars, Salts, Cloth, Gems, and Rare Raw Goods.
Religious organizations will want artifacts lost to the church, the locations, and or bodies of important figures. They will also want to capture the same items of religions antithetical to their beliefs for destruction. Art, Books, Cloth, Statues, Icons, Emblems, and Weapons.
Nobelity will value display above all and want to track the latest trends. Art, Jewelry, "Perfect" Gems, Luxury Objects, and Weapons.
Illicit or Secret Organizations will want items of power that align with their agenda: Books, Weapons, Artifacts, and Magic Items.
WHO CONTROLS WEALTH EXCHANGE?
Crown- will take 30% at the door
Local Lord- will take 20% at the door
Guilds- will take 25% of any sale within the confines; 10% from members (membership esoteric)
HOW TO SUBVERT CONTROL OF EXCHANGE?
Develop standings and status among those who want items and control wealth exchange
Thieves guild- will smuggle and help you avoid all the above for 25%
Fences will sell goods quickly, quietly, and/or maximum value (pick two). Not quickly means PCs will have to wait (one complete adventure maybe); not quietly means PCs will draw attention from Illicit or Secret Organizations; not max value means PCs will get less gold.
WHAT CAN BE DONE WITH IT?
Fighters: Building a castle and raising troops takes gold, but before that it requires status, and for that, you must look the part and been seen as nobility.
Thief: The guild will require payment, but status in the guild will require increasingly more daring heists and increasingly rare items.
Clerics: Tithes and shrines must be built. Also, holy symbols made from various material symbolically connect to the gods will increase spell casting and the chance of miracles.
Wizards: Spell components can increase casting power, duration, and prevent spell slot loss. The component must have a symbolic, mythological, or alchemical connection to the spell being use. Each component takes up 1 slot of encumbrance as it has to be preserved and easy to reach.
Elves: Similar to Fighters and Wizards, but value magic items above all else.
Dwarves: Much the same as Fighters, but value relics and symbols like Clerics. Gems prized, pearls hated.
Halflings: Like Guilds, value rare and raw goods. Value books, fine cloth, luxury goods, but gifts given above else as a symbol of experience and community.
WHAT ARE SOME EXAMPLES?
The wizard, Mayfly, is trying to work out how to bypass a lake horror that guards the bridge to Black Keep. Mayfly decides to create two potions of Flesh to Stone but add bile from a cockatrice and salt from the ground marble of a medusa-made statue.
EFFECT: Since Flesh to Stone gives a save throw, the DM rules the inclusion of the bile and salt causes that save to be made at a -4.
The thief, Fetch, wishes to receive divine protection against misfortune on her next sojourn to the Black Keep. Fetch prays at the temple of the Crow, god of the Wheel of Fortune & thieves & Kenku, and offers a jade ring and a ruby ring (both stolen). Jade is associate with the lost Serpent empire and ruby is associated with the heart.
EFFECT: The DM gives a positive sign to the thief (murder of crows swirls around them) and (secretly) gives them +4 to their next save (heart) vs. Poison (Serpent empire) roll from any source.
The fighter, Redd, has decided to entreat the local lord for the land around the Black Keep. After all no one is using it, what with all the death. They decide that because the lord is known for his strict adherence to protocol and formality, they will spend gold to: commission a new shield, clothing, and buy a quality horse & tack. Redd also brings a gift for the lord's high consort & seer: a book of astrology from the Black Keep.
EFFECT: Reaction roll is low: Because the fighter carries themselves in a manner befitting of a knight, the lord denies the land but agrees to confer a title on the fighter. However, they are approached later by the high consort, because of the gift, who has some information about the Black Keep.
The cleric, Fish, is concerned about the demons hold the throne room of The Black Keep. Fish decides to sanctify two bells in order to ring them when demons are speaking-- potentially breaking spells of corruption, lies, and charm. One pure silver bell is made from the silver rosary worn by the head Abbess (but Fish has to go on a quest in repayment) and the other two-handed great bell is made from the wood of a pulpit Fish saved from destruction.
EFFECT: Both bells are made of materials that reinforced the theme of Fish's diety. The DM rules the small one maybe be rung to remove a spell cast by a low-level demon. The larger, because its made from a pulpit, must be rung continuously but also the player of Fish must make sermons every round (CON check) to counteract a spell.
