A display system may include a display, a first server transmitting first content to the display device, a second server receiving the first content from the first server, and a camera transmitting second content obtained by capturing images on the display, to the second server. The second server may be configured to determine whether a rate at which the first content coincides with the second content is greater than or equal to a specified value, by comparing the first content with the second content. The second server measures a first time period during which a region of the captured images corresponding to the first content coincides with the second content at a rate which is greater than or equal to the specified value. Advertising costs are calculated based on the measured first time period.