Discrimination

If most people were to stop buying NX cards in favor of the MTS (because it's easier and requires no money), and people bought items like keys, event tickets, etc, then wouldn't the flow of NX from MTS eventually slow, and no one could get any good amount of NX from there? Then it would be back to NX cards/ paypal.

The NX cycle (I just call it that) will eventually force pre-existing buyers to buy NX to fill in the void.

In the events debate, I would have to side with Bacon. They are meant to be fun, regardless of the level (unless, it's 10 or something). Does merchanting on the MTS sound fun? To me, no, and it would not benifit me in any way. Since Cash items expire, regardless of what I look like, they are worthless. Pets require maintenance, and those quests for wanted scrolls don't repeat, thus I don't get a continuous NX flow to fund them every time they expire.

Obviously, they're not repeatable. The quests are there as catalysts to get you started on the path that will allow you a continuous income.

I don't have the time nor the mesos to scour the FMs for bargains. So, why, then, should some of these events almost require NX?

Because the US is a capitalist country. Nexon is a company trying to make a profit. Why can't they have a right to host an event that they want? It's not like all events are like this, and this key event is benefiting the average players in many ways:
1) Driving down prices so that the common player who doesn't have time can actually afford some of the items.
2) Increasing item supply, allowing the common player an easier time scrolling. I remember before dark scrolls and everything else, it took me 13 full levels to fully scroll my Maple Lama Staff. 8/74 at the time was considered godly (anything over 7 is godly, because most people back then scrolled with 60%s). Now it's almost nothing. And in the future, what we have now might be worth less. So that's benefiting the average player to you.
3) Decreasing money in the system. More trading means more taxes means more money taken out means less inflation.

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So, why, then, should some of these events almost require NX?

So, why, then, after giving so many variations of the explanation, should you feel the need to ask the question yet again.