Those numbers are by assuming you have a dedicated player base always willing to join you on the game every time you're ready to turn your console on and sit down for three hours grinding like hell. Also, Nightfalls NEVER guarantee an effing thing. I stopped doing Nightfalls altogether. Two other friends get exotics while I get Ascendant Shards after an entire hour of battling? I don't effing think so. And Iron Banner does allow purchase of them, but not everyone is a huge fan of Destiny's PVP. Plus, there are many requirements in Prison for the achievement of etheric light to fall into place. Not to get kicked from Destiny servers at the time when you're not allowed back into the game. Everyone must stay together through the entire thing (nobody quit). Obviously maxed out weapons help a lot. Everyone has a mic for proper communication. And it's pretty damn frustrating being unexpectedly teleported during a boss battle (basically forces you to a death when the team can ill afford you to die)