The headline price is a market signal
Simconomist broad-market pages use the headline price reported by the Sim Companies market ticker. It is not an average, and the ticker does not identify the quality, quantity or seller behind that price.
When Simconomist has measured a full order book for a product, it can separately show supply, listing count, liquidity and quality-specific prices. Those fields stay unavailable when they have not been measured.
Quality
Goods are listed at a quality level. A buyer who needs at least quality 2 can be satisfied by anything of quality 2 or higher, so the effective price of "quality 2" is the cheapest offer at quality 2 or better — sometimes that is a quality 4 lot someone is clearing cheaply.
That is how prices are calculated throughout this site, and it is why a higher quality occasionally shows a lower price than the one below it.
Supply and liquidity
Supply is how many units are on offer in total. Liquidity, which we score from 0 to 100, combines that depth with how many separate sellers there are.
They are not the same. Ten thousand units from one seller is fragile — that seller can withdraw and the market empties. The same volume across forty sellers is a market you can actually rely on.
Volatility
Volatility measures how much a price bounces around, expressed as a percentage so that a $0.50 product and a $500 product can be compared directly.
High volatility is not automatically bad — it is where the opportunities are — but it does mean that a profit calculation done now may not describe the situation in six hours.