Yes you do need your own Google Maps API Key. So people can see your deployed map. Each account comes with a certain amount of free map loads on the editor to get you started. Google is giving $200 credit PER MONTH on Google Maps API usage. This is enough for most websites. (As of the date writing this)  Unless your website have over 900 map loads a day, you should not be paying anything. (Most businesses don't get this kind of traffic.)