Trading will cost either hams or irons, or maybe both. Some of the players could have excessive ham and iron, so they could use them to trade for farmable items.
For example maybe 10000x iron for 3* ingredient like midnight roots or 1000x ham for 1* ascension materials like adventure’s kit.
And if the player have excessive farmable items for example like training manual and oil, they can trade in to get ham or iron probably 1/3 of the trading price.
**Also, this is not about trading between players. It’s about an idea for a new building.