La valuta come materiale di crafting, non come portafoglio
The unusual part of this game is that the trading unit and the crafting material are the same object. An orb spent on a trade is an orb not spent on an item, and every purchase competes with a craft. That is why orders in Path of Exile 2 currency are sized in orbs against a plan rather than as a round number.
It also explains why finished gear is often cheaper than making it. A craft has no guaranteed outcome, while a listed item has a known one, and the difference between them is the price of the failed attempts. Comparing an Path of Exile 2 items listing against the orbs a craft would cost is the calculation worth doing before you spend.
The rule most players settle on is to buy the pieces that gate progress and craft the ones where a partial result is still useful. The escrow behind either route is described in the Eloboost24 buying guide.