While messing around I realized (I could be wrong) that production cost isn't just that nice low number next to the product/produce. It's the cost of all components together. So I set up a small excel sheet to keep track of things.
For instance - Potatoes. The total price of 1kg would be 1.35c after adding up total seed production cost (water+prod. cost) and total potato cost (water+prod. cost).
Note: I add cost for water because I have insufficient funds to build my own well, and need to go shopping once in a while.
So I worked out some prices, for my shop, +50% price, and +50% price + commision fee.
I thought I was on a go. Then I had a look at the market and it's ... all over the place. I can only grow Q0 at the moment so I kept looking at that. And in my imagination, better quality should generate more money. But the price range of Q0 are sometimes higher than let's say Q1. ...and looking at pigs, they're not even selling for 1/2 of total production cost (233,05c)
Then I had a look at cotton (just for kicks) in the purchase section of the forum, and someone is buying for almost 1/3 of the total cost I calculated.

I could probably improve my business without using the market, and just produce everything I need and sell it in my shop. But it would be nice to interact with other businesses. Especially producing contest stuff.