
Rikus, considering how much you played (four chars level 70+) and I did (one char level 90, my three others are around 20 to 30) I think we could be in a similar situation as for gaming time (for me, 3-4 hours a week, but as much to trade).
But I started trading at mid-Nightmare with my main, so really early.
Now, after 200-ish sales and purchases, I am clearly in the third part of your post, even if clearly less rich than many of the users here.
The goal is not to brag at all, just to say that ALL my Wealth is built on tradings.
Set pieces, bases bring me pgems and mid runes. Countess also is a great place to farm for mid runes and gems.
40 pgems -> Ist, 15 PAmethysts -> Ist, 25 Rals -> Ist are trades that I did several times each.
And after that, DClones killing brought me Annis, kept the best ones, sold the others. The source may vane now with the ladder Annis coming, but anyway it has brought a lot up to now.
Also sold quite a lot of keys. And geared up. And have been also helped by richer generous players. And have to say the community of this side has always been welcoming and nice to me.

As for "natural" runes seen, I have seen one Ohm (in 3 p with my two comrades, so "shared" loot), one Vex (same), and one natural Ist solo (Countess, gave me one Mal too). One of the two buddies got Gul at Hellforge. Everything else is below Mal.
tl;dr : trading is the path to e-Wealth.

Necrarch
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