@ayewo nails it. See her/his answer. I just want to add that while it might be possible for you and me to "build this in a weekend" (although in reality it alw

@ayewo nails it. See her/his answer. I just want to add that while it might be possible for you and me to "build this in a weekend" (although in reality it always takes longer considering all the edge cases), for other businesses it might be cheaper than just buying an existing app. They know what they are getting versus hiring a freelance developer, writing a spec, managing them, etc, etc.