How can you model/simulate the price/value of a good?
You're question is unclear...

If you're in a competitive market, as a supplier, you can only see the market price at a given time, where it is set essentially by all suppliers and consumers at once

If you're a monopoly, then you can estimate the quantitive demand based on price, simply because you control the entire market, and set the price level at the marginal revenue, where you gain the most

The only ways, other than a monopoly, to estimate demand are:

If demand is completely inelastic, like with fuel: people won't change their driving patterns on marginal changes in price
meaning quantity will remain the same in any case 

completely elastic: price will remain the same no matter the quantity

A government set price, quantity or any other specific regulation on the product. Although, with "too much" regulation, in some cases a black market can be created, etc.