Gold Dupe with No Mods
You will need some gold to start.
Even just a few hundred will be fine, this works with small items as well.
but due to the nature of the dupe, it is better to use higher-value items.
I also recommend increasing your reputation with the vendor, and or using a Charisma-based character. They will have higher Selling and lower buying costs.
Not required, just makes it more efficient.
Find a vendor with a substantial list of items for sale.
I find armor to be good, and weapons as well if the vendor has enough of them.
We want items that do not stack. Scrolls and things can work, but because of the nature for them to stack those are not ideal.
In your inventory, you want a section that has a long line of items that are not stacked, and then one item that is. In my inventory, I will buy some armor, and at the end of the armor in my inventory, there is a stack of arrows. It can be anything that stacks, as long as it is in line with the items you’re selling.
Swapping to Barter Mode, we can start the dupe. My game runs fairly well, but I induce lag with Chrome and other applications to slow Baldur’s Gate 3 down. Open tabs in Chrome or play video files. Anything to slow the responsiveness of the game. The slower, without crashing, the better.
You will need an auto clicker. I have mine on my mouse, and it clicks once every .01 second.
now line up your cursor on the first time in the list of items you want to start to sell. The game will move the rest of the items up as they are sold. However, because of the lag in the transaction, you will be able to sell multiple copies of the second item, as well as the game lets you “buy it back”
Slowly, the game will sell each item, and then when you hit your stacked item, the popup for selecting how many items will let you know the chain is complete.
Repeat forever. I suggest saving often, as this is likely to cause crashes.