startGas = 1,000,000
gasPerOrder = 100,000 (so fulfilling an order costs us 100,000 gas)
ordersLength = 10
startGasPerOrder = 900,000 + ((1,000,000 + 20,000 - 900,000) / 10)
startGasPerOrder = 912,000
startGasPerOrder = 200,000 + ((1,000,000 + 20,000 - 200,000) / 10)
startGasPerOrder = 282,000
uint256 gasCost = (startGasPerOrder - gasleft() + wethTransferGasUnits) * tx.gasprice;
# 2nd order
# gasleft() is 800,00 because we said that executing the order costs ~100,000 gas. At the beginning of the order, it was 900,000 so now it's 800,000. This makes the computation a little more straightforward although it's not 100% correct.
gasCost = (912,000 - 800,000 + 50,000) * 1
gasCost = 162,000

# 9th order
gasCost = (282,000 - 100,000 + 50,000) * 1
gasCost = 232,000
