Look, maybe I didn't use the best of examples. But I said I have the same issue with any kind of product I try to sell, in any town.
To be more clear, I'll use a general example. Let's say I have 40 pieces of product X that I bought with a medium price of 34 per piece. So in my inventory it is marked 34 as the value of a piece of this product.
I find a city where I should sell it and make a profit. It says that it buys one piece of the same product with 76 per piece. Now, I try to sell piece by piece (one piece at a time; I normally do this to see when the price drops too low). When I sell the first piece of product, the price of the product drops to 34 (it equals the value of the product from my inventory). This happens with any given product I try to sell. What is even more strange is that the money I get from selling my one piece of product is not 76 but 34.
Someone said that I should try selling the whole quantity of product not piece by piece. I will try this, to see if it works.
And please don't tell me I don't understand the concept of supply and demand. I don't need to be a Ferengi to understand how the trade should work in this game.