Trading

Selling Items
All items can be sold to a vendor for half it's market price, regardless of whether they are mundane or magical. If you own a stall or shop in a settlement - you are able to sell wares you have made at full market value.
Jewels
Jewels in the world fit into one of 3 sizes and are valued based on size - small (50 gp), medium (150 gp), large (500 gp). All different kinds of jewels, whether it be a ruby or diamond - are worth the same. Jewels of more irregular and higher pricing can exist.

Creature Harvesting
When attempting to harvest a particular part from a creature, you must succeed in rolling a DC 20 nature skill check. When you successfully harvest the item - you essentially gather a "creatures worth" of that item, which is always worth 10 gp each. This price is negotiable if said creature parts are being sold in a stall or shop of your own, rather than selling to a vendor. If your intending to harvest poison from a creature - on success you gain access to a dose of that creatures poison - the price is as listed in official source, or determined by DM. The harvesting requires 1d6 minutes - If the character fails the check by 5 or more, the character is subjected to the creature’s poison. If what is harvested is used as a material for the crafting system - it's cost is the 500 gp that those materials are worth and follows the "Selling Items" rules.

Charisma
For each point of modifier you have in charisma you gain an additional gp when selling and a discount when buying items either with a vendor or from your own stall/shop. 5% per point of modifier.

Owning Property and Building Structures
Shack/Hut, Small Apartment, or a Stall 1,000 gp/6 Days
Small House/Cottage, Large Apartment, or a Small Shop 2,500 gp/15 Days
Medium House/Stead, Chapel or a Large Shop 5,000 gp/30 Days
Large House/Manor 7,500 gp/45 Days
Small Keep, or a Temple 10,000 gp/60 Days
Large Keep 25,000 gp/150 Days
Small Castle/Palace 50,000 gp/300 Days
Large Castle/Palace 100,000 gp/600 Days