These are expressions used by what Osakans would affectionately call a 「kotekote」 (over the top) old guy from Osaka. In anime and manga, Osakan characters using Osaka dialect are usually portrayed as shrewd businessmen or frivolous moodmakers who readily get along with other people. Alongside stock Osaka-dialect phrases like 「~ya de」 (~you know!) and 「~chau」 (it isn't~), in business situations a polite style is also used, including expressions such as 「~desse」 (I tell you~) and 「~massharo」 (~isn't it?).