A word that encompasses buying and selling?
My first thought when I saw “buying and selling” was trading (independently of coleopterist. The verb trade covers both bartering (trading when both parties put forth goods or services) and buying/selling (trading when one of the parties puts forth money).
In context, this seems to be specifically about evaluating the price. I believe the term generally used in this domain is appraisal; valuation or pricing are used with a similar meaning in other communities.