Well I do not know for sure how it works.
But there are some guide lines. If demand> supply, then 1.5x works. Other way round, then I "think" consumers would choose to buy cheaper products, relating to product QL too. When prices of two different players are the same, it chooses randomingly who sells and how much. Products with higher QL can have a higher price and consumers won't care "too" much.
You cannot exactly calculate the prices. You have to observe demand and supply and after a while, if supply is higher prices decrease.
There are some products, where prices decrease faster. It is possible to sell cars a long time at maximum price although supply is higher. Motorbikes decrease faster. Just an example, I observed the last two rounds.
In general you need experience to find the right price and modulating the prices bit by bit will help you to find the real maximum price.
okay guys thanks for the help 
