This is obviously an exploit. It doesn’t work on everything but they say it works on all metals and most leathers. It does not work on herbs.
- Open your inventory then select the item you want to duplicate. Move it to Valuables. On PS4, that’s done by pressing L2.
- Go to a vendor then proceed to sell. Go to Valuables and press Sell All then Sell individually in quick succession. On PS4, that’s Triangle quickly followed by X.
- You’ll know you did it correctly when the item disappears, indicating a successful “Sell All”, and you get a window prompting you for the number of items you want to sell.
- Go to the buyback screen. You should be able to buy back double the number of items you sold originally.