Serious questions about gold/trading prices

Ok, first, i do not trade in D4 but i have some questions about the market there.

I would call myself a more than casual gamer. Definitely not 24/7 but some hours a day.
I never had more than 300-400 million gold at a moment. I masterwork and craft some gems (bcs it annoys me to hell, to see these fragments laying around everywhere) and voila, out of cash once more.

So how do prices like 2b or such sums, that pop up in the trading channel can be “achieved”?

I have this weird Diablo 3 feeling, where you needed in the first game at the first months a inferno yellow item to even get a zombie killed. These items were sold for millions of gold in the market. As a player, coming from nightmare 200k was the maximum me and my friends had. Repaircosts and so on. My solution in the old days was to switch to hardcore. there the same item was sold for 5k-10k gold.

So how do casual players reach 2 billion for example?
Bcs the 24/7 players, that could afford these prices, they don’t need the item, bcs they have even better ones in most cases.

Are these prices nonsense?
That is my feeling.
But on the other hand, i only see such numbers in the trading channel.

Thx for serious answers.

The players buying and selling these items, have gained the currency to do so by trading.
The prices are generally what you would see on the trade site.
I have sold items for billions quite a few times.

Swipe credit card. Gold farmer bots.

Pre-horde, whispers was my go-to for gold as they are relatively quick and each dropped several million gold. Hordes made gold extremely easy to come by, and I think that’s when inflation hit. As for now, I fear Soluss may be right - hordes seem to have had gold nerfed substantially and my guess is they are around the same as whispers now. But also I’m running around in torment 2 clearing out sidequests and dungeons and I’ve casually made a couple dozen million over an evening, so perhaps high-end play can actually push prices to nonsensical levels still.

Whispers and the arena are also my way.
I’m T4 but 800 aether gives you 12 million gold. And you do not get 800 aether every time. Only if you hit the “hellbourne hunting” and “hellbourne+1” spawning. I spend my 200 for the chest every time.

A billion, i never reach this amount.