I would like to adapt the selling price of the product and implementing some conditions based on its buying price and the public price. Here is the process flow and how it should work. 

1. customer requests us to make an offer
2. We create a call for tenders and send RFQ to the given suppliers. 
3. select the cheapest
4. create the offer. The price of the offer should be a price between the buying price and the public price. The public price is the price at which the customer can directly buy the product. (e.g. let's imagine the public price is 100€, If I get a price of 85€, the price proposed should be 95€ but if I get a price of 65€, the price can be 90€.)

Concretely, I would like to set the selling price of my product for the specific order such that the customer get every time 10% discount on the public price except if we get less than 20% discount ourselves.