The Witcher 3 Item Duplication Glitch
Go to any monster nest and loot everything in the nest except for one item. You can leave any item, but you must leave one item or this will not work. Walk a short distance away from the nest, and then loot the nest again for all items to have respawned. Repeat this as many times as desired. Sell all the items you get from this exploit for lots of crowns. The game has a cap of 65,535 crowns. Thus, stay under that number to avoid losing any crowns. If you meditate for five days, the shops will get all their money (crowns) back. Alternately, go to the Loan Shark in Navigrad since his money comes back each time you leave. You can also buy florens so he has more money, and then just convert florens to crowns at the bank in Novigrad.