The second thing you've perhaps noticed is that the prices are not round numbers, and it is impossible to split cheap poe chaos orbs items into parts - so what does "0.23C" mean?
The trick is simple - most trades involve volumes larger than 1 of a currency item. In reality the rates are:
8C -> 25alc
70alc -> 16C

The C->alc side is clear - 8 is the lowest number you can multiply both sides by and get round numbers, but the other direction could be written as 35alc -> 8C to get the same result - so why? This is where the "price of exchange" plays a role.

I have 2 goals while trading currency in the long run:
- Maintain an approximately even rate of inflow and outflow for each currency.
- Make sure I earn at least 1C of profit per trade (on average) - otherwise the trade doesn't overcome the friction of exchange.

And I have 4 "dials" to fulfill buy poe chaos orbs :
- Exchange rate for C -> alc trades.
- Exchange volume for C -> alc trades.
- Exchange rate for alc -> C trades.
- Exchange volume for alc -> C trades.
BY https://www.playerhot.com/games/path-of-exile/Golds here now... well done, so thanks!