Eggs? You can offer to buy and sell stocks at whatever price you want. You just won't complete any trades if you offer to buy at $1 and sell at $1,000,000 dollars per share. If "supply and demand" didn't exist, you could become a millionaire in one trade.

Although, I suspect what this person means is: many markets are not free from price collusion. The stock market is very liquid because there are many buyers and sellers. You literally cannot corner the market because it would require too much money, and it's illegal.

This creates quick movements based on news and sentiment. Food prices do not operate this quickly, but they do move based on available supply and demand.

Other markets have much more collusion. When there are only three producers, collusion is inevitable. If one seller raises the price and still finds buyers, the other two will follow without any communication between them. The solution is doing whatever you can to not buy what they are selling. Demand moves markets, not supply. They are raising the price because people are paying it.

Also, better regulation from the FTC would help.