How do I find the actual sales price of 389 peterbilt?

Umm, ask a Peterbilt dealer? That question has many answers, the price varies wildly based on exact specs, condition and even who is buying it. A fleet pays a much lower price per truck than a single owner operator.

Then there is Federal Excise Tax (FET), possibly state sales tax, title/tag/doc fees, etc. If you are just tire kicking or trying to see if someone is giving you a good deal try searching on Truck Paper, it will give you a comparative idea of prices for similar models. New trucks rarely have prices posted online because of all the above variables.

If you are looking for NADA or Kelly Blue Book values, they do not exist for the heavy truck market, simply too many variables with each truck and all the options to be of any real use.