Path of Exile has done away with a single unified currency entirely. Seeing as how every player is a shipwrecked survivor inhabiting a hostile land, that definitely makes sense from an in-game perspective.
The problem is, there's no way to tell what anything is worth, or which items are worth more as part of the local economy.
The merchants give you Scroll Fragments for white items, so we can sort of divine that that is the base item value. But it doesn't really flow well from there, as unidentified magic items give you Transmutation Shards, while apparently identified magic items give you Scroll Fragment(s), thereby losing 80% (or less, as you get higher level stuff) of the value, just by identifying the item.
Identified rares give you Alteration Shards, yet another item type. By taking a look at the purchasable items that Nessa has, I have figured out the following:
Item Cost Cost in total Scroll Fragments Scroll Fragment 1 1 Scroll of Wisdom Scroll Fragmentx5 5 Portal Scroll Scroll of Wisdomx3 15 Orb of Transmutation Portal Scrollx7 105 Orb of Augmentation Orb of Transmutationx4 420 Orb of Alteration Orb of Augmentationx4 1,680 (!!)
That gives me a good baseline, sort of, but there are quite a few orbs past that. Where does the Orb of Alchemy fit in? Orb of Chance? Chromatic Orb? Or heck, let's get crazy, and add in the Armorer's Scrap and Blacksmith's Whetstone! Or they worth anything in the local economy at all? How can I figure this whole thing out?