During World War I, publication of the guide was suspended. After the war, revised editions of the guide continued to be given away until 1920. It is said that André Michelin, whilst visiting a tire merchant, noticed copies of the guide being used to prop up a workbench. Based on the principle that "man only truly respects what he pays for", Michelin decided to charge a price for the guide, which was about 750 francs or $2.15 in 1922. They also made several changes, notably listing restaurants by specific categories, adding hotel listings (initially only for Paris), and removing advertisements in the guide. Recognizing the growing popularity of the restaurant section of the guide, the brothers recruited a team of inspectors to visit and review restaurants, who were always anonymous.