Item crafting requires tool proficiency, half gold and time

Magic item crafting additionally requires Arcana proficiency, more gold and time.

Buying Magic Items

Magic items costs are determined by the Magic Item Values by Rarity; Magic Item Rarities and Values table. These costs are in addition to the cost of a non-magical variant.
Cast-Off Scale Mail would cost 150gp to buy. 100gp from the magic items table, and an additional 50gp from the cost of Scale Mail

Official Rules (summarised):

Crafting a non magical item requires the relevant tool proficiency, half the cost in gold (materials), and time equal to the (original cost / 10) days.
- A Scale Mail costs 50 gp, so would take 25 gold in materials and 5 days
Crafting a magical item additionally requires arcana proficiency, and takes additional time and gold based on the rarity.
- Magic Item Crafting Time and Cost
An uncommon scale mail, like Adamantine Scale Mail would take an additional 200gp and 10 days to craft for a total of 225gp and 12.5 days
Helpers can halve this time, normally only one character can assist with crafting, but the DM may allow more assistance.
- This would take the Adamantine Scale Mail from 12.5 days to 6.25 days
Some abilities allow halving the time yet again, such as certain Artificer subclasses. an Armorer artificer can half the time spent crafting magical and non magical armor, therefore bringing the total for Adamantine Scale Mail with one assistant from 12.5 days to 3.125 days
One day is 8 hours of continuous work. RAW this is a complete day dedicated, however I will let work of at least 1 hour to contribute to the total, and work between 8 and 16 hours to give a level of exhaustion, so a short adventuring day could contribute 2 hours to the total, races that have short rest times can contribute relevant time to item crafting (such as Elf’s 4 hour rest)

Magic items of rare or higher quality require a quest or additional gold to find specific components.

As you need raw materials, you need to declare this whilst shopping. in most shopping districts you will find what you need.
- In small towns < 400 people, the components for magical items are likely not available. roll a D6. on a 1-2, you cant find all the parts required to start crafting, on a >3, you find all the parts required.
Magic items of Rare quality or higher will require a special component found only in specific stores, or found through quests.
- If bought through a store, the magic item cost will require an additional 250gp
- if found during a quest, the total cost will be reduced by 250gp
- Examples:
  - a Flame Tongue might require a heart of a Fire Elemental
  - Cloak of Displacement requires fur from a Displacer Beast
  - Dragon Scale Mail requires scales willingly given from the relevant dragon.

Magic Item Balancing: