Random drops are not earning, but a lucky chance after hours and hours. Xur takes coins earn by chance an some strikes that guaranteed them. Then he trade those coins for guns "Earning" and "xurning" are both legit. Although xur guns should be more expensive. Because playing strikes for a week does not guaranteed an exotic. However, waiting for xur for a week n palying 2-4 strikes will guaranteed the coins to get an exotic