What is the ruling on selling goods at a higher price according to market value and giving a sum of money to the official who informed me about the price increase, and is it permissible to give him from zakat funds?

There is no objection to raising the price of a commodity according to market rates, as there is no specific profit margin mandated by Shari'ah. If the buyer and seller agree on a specific price, then there is no harm in it. As for the money given to an employee for his expertise in price fluctuations, it falls under the category of ju'alah (a promised reward for a specific task). It is not permissible to give it to him from Zakat funds, even if he is poor, because it is in exchange for a benefit to the muzakki (the one paying Zakat), while Zakat is a right of the poor.