It will cost you 1 Forge Point to fulfill a trade offer. Note that only the player that accepts the offer will have to spend 1 Forge Point; the player that created the Trade offer won't. In guild-only trading, no forge point is needed.
You will receive 1 Forge Point every hour up to a maximum of 10. Should your Forge Points reach the maximum of 10, the timer will stop and start over from 1 hour once you have 9 or fewer Forge Points, therefore it is highly recommended that you spend your Forge Points as often as possible.
At low level Bronze age/Iron Age, it is not worth it to buy them for coins, as the prices quickly become abnormal. At that level it is best to wait, and get a full bar every night-time.
Buying Forge PointsIt is also possible to buy Forge Points with either Coins or Diamonds.
It costs 50 diamonds for each expansion. You may buy the first Forge Point for 200 Coins, and thereafter the price will increase by increments of 50 Coins per point. In the diagram below, the cost of FP has risen to 11850 Coins, from the original 200 coins.
Forge Point Purchase Cost Formula
In determining how much X amount of Forge Points will cost in terms of coins (Y), use the formula:
Y = X(initial amount to purchase)+50(X(X-1)/2)
y = 25x2 + (Initial Value - 25)x
For example. I need 23 Forge Points to finish researching a technology. My starting cost is 3000 coins.
- Y = X(3000)+50(X(X-1)/2)
- Y = 23(3000)+50(23 x 22 / 2)
- Y = 81,650 Coins.
- Y = 25(23)2 + (2975)(23)
- Y = 25(529) + 68,425
- Y = 13,225 + 68,425
- Y = 81650 Coins
The equation is built upon the fact that purchasing a FP increases by +50 coins every time you purchase one.