Post-Auction Valuation*
Once the auctions are over, the game updates the value of goods to the average price of those goods that was traded that turn, whether it was to the Store itself, or between other players. This only happens if there was at least one of that good changing hands.
This is a very important step as it reflects the latest market value of all goods, which can affect your score (and therefore your turn order, which is crucial for letting players catch up, and increasing the challenge for the leader). NOTE: This does NOT happen in round 12, because of an obvious exploit that existed in the Atari version (fixed in the Commodore 64 version) which lets two players exchange a single unit of a good at a substantially high price, re-valuing their goods, and vastly inflating their score.
Actually, I'm quite certain that this exploit was /not/ fixed in the Commodore 64 version, as I rather distinctly remember discovering how to do precisely that to ensure a maximized score. It only worked if another player cooperated, though, and I'm not sure whether it worked for anything but Crystite.