Pricing & Fees

The Twin.fun bonding curve determines deterministic pricing for every trade.

Fees per Trade

• Protocol fee → sent to the treasury address.
• Subject fee → paid to the twin owner.
• Percentages are configured in the contract (1e18 = 100%).

Creation Rules

• At zero supply, buyers must purchase at least minSharesToCreate keys.
• If an ID is pre-mapped to an owner, only that address can execute the first buy.

Pricing Intuition

• Earlier buyers pay less; each additional key marginally increases price.
• Selling walks back down the curve, returning ETH at the lower supply point.

Mathematics (Advanced)

Let supply be the current supply and amount the delta for the trade.

sum1 = (supply-1)*supply*(2*(supply-1)+1)/6         // if supply > 0 else 0
sum2 = (supply+amount-1)*(supply+amount)*(2*(...)+1)/6
price = (sum2 - sum1) * 1 ether / 1,600,000

• Buy: getPrice(supply, amount)
• Sell: getPrice(supply - amount, amount)
• Fees:
  • protocol = price * protocolFeePercent / 1e18
  • subject = price * subjectFeePercent / 1e18