arbitrage flashloan profit

profit.js

...
                const oneSplitRates = {
                    buy: new BigNumber(oneSplitResult1.returnAmount * unitRate).shiftedBy(-toTokenDecimals[j]).toString(),
                    sell: new BigNumber(oneSplitResult2.returnAmount).shiftedBy(-fromTokenDecimals[i]).toString()
                }
                console.log(`1inch Exchange ${targetTokens[j]}/${fromTokens[i]}: ${JSON.stringify(oneSplitRates)}`);

                let profit = (oneSplitRates.sell - oneSplitRates.buy);
                // profit needs to be eth price
                if (fromTokens[i] != 'WETH') {
                    profit = profit / ethPrice;
                    console.log(`Profit: ${profit.toString()}`);
                } else {
                    console.log(`Profit: ${profit.toString()}`);
                }

                if (profit > 0) {
                    const tx = flashloan.methods.initiateFlashLoan(
                        addresses.dydx.solo,
                        fromToken[i],
                        toToken[j],
                        amountFrom
                    );

                    const [gasPrice, gasCost] = await Promise.all([
                        web3.eth.getGasPrice(),
                        web3.eth.estimateGas({data: tx.encodeABI()})
                    ]);

                    // a return cost
                    const txCost = gasCost * gasPrice / 10 ** 18 * 2 * ethPrice;
                    profit = profit - txCost;
                            
                    if (profit > 0) {
                        console.log(`
                            Block # ${block.number}, ${targetTokens[j]}/${fromTokens[i]}
                            Arbitrage opportunity found! Expected profit: ${profit}
                        `);
                        const data = tx.encodeABI();
                        const txData = {
                            from: admin,
                            to: flashloan.options.address,
                            data,
                            gas: gasCost,
                            gasPrice
                        };
                        const receipt = await web3.eth.sendTransaction(txData);
                        console.log(`Transaction hash: ${receipt.transactionHash}`);
                    } else {
                        console.log(`
                            Block # ${block.number}, ${targetTokens[j]}/${fromTokens[i]}
                            Arbitrage opportunity not found. Expected profit: ${profit}
                        `);
                    }
                }
...