Moonlighter
57 Achievements
1,000
25-30h
Evil Merchant
Sell 20 items slightly overpriced
12
6.8%
How to unlock the Evil Merchant achievement in Moonlighter - Definitive Guide
Vines slightly oversell for 5 coins and Roots for 8.
You can always check your book and see if you have found any prices slightly over in your sold items and use that as a guide as well.
This achievement is a bit random, but you'll easily get it as you try to figure out what things should cost (unless you're using a guide for that). Even though an item might be overpriced, and the customer reacts poorly, they often still bring the item up to the counter and buy it anyway which is what goes toward this achievement. Check the Road Map for the face you're looking for.
To know if you are selling an item slightly overpriced, when the customers come looking at your merchandise, you will notice their expression to be a bit irritated when they pick it up. When you sell it to them, you will get the notice that the demand for it has lowered. You should get this throughout the course of the game by just adjusting to find the right price to sell your merchandise.