Need explanation here

You said that the true market value of a company is the market value of the shares on the stock exchange and not the market value of net assets. For instance, if a company has the following net assets: Share capital = $100,000 Share premium = $60,000 Retained Earnings = $300,000 Revaluation reserve = $50,000 Total equity = $510,000 The market value of the shares in the stock exchange is $150,000 then according to this the market value of the business is $150,000 which is the shares value traded in the market at the time of the sale of business? But the actual worth of the business should be $510,000 because the value of our assets is equal to the total net assets (isn't it?) Thank you!