Looking in the books is good. Looking in the right topic is better.
Feat: Craft Magic Arms and Armor (PHB, pg. 81)
Creating Magic Items (DMG, pg. 241)
Creating Armor (DMG, pg. 243)
Special Materials (DMG, pg. 242)

Basically, the creation of a (non-magical) Dwarven Plate follows the Craft skill rules. It takes as long as crafting a masterwork full plate, but costs as (standard full plate plus 9,000 gp), according to DMG pg. 242.

Now, you or another character with the Craft Magic Arms and Armor feat can enchant this armor to +1 Dwarven Plate (Base price 1,000 gp). It would cost 500 gp (1,000/2) and 40 XP (1,000/25). It takes one day (1,000/1,000 per day; round up).

The market price is 11,500 gp (10,500 + 1,000 gp). If you buy it, you pay the market price. If you sell it, you get half of the market price.

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