Participating in an event, for an agreed upon compensation. It is the only form of earning. This could relate to folks in the real life, who sit in the break room for 50 minutes of each hour, and get a paycheck, then go buy an iPhone. That is still earning wages. To get something from RNG, is the same as winning a lottery. It is random, and no guarantee. Could you imagine racing for something, placing 1st, but then encountering the Marshall who then says,"Sorry, we're going to give the 1st place trophy to the guy who came in............ ............. 5th!" Xur is the horribly implemented attempt at balancing that out.