How to calculate the gas cost of Solidity's 'transfer'?

Question

I have read that the gas cost of transfer function is 2300Ether. I have got the following contract having a function, testFunc(…), only containing transfer method as shown below, because I want to calculate the cost of 'transfer' function:

pragma solidity ^0.5.1;
contract TransferCost{
   uint public testVal = 97 ether;
   function testFunc(address payable addr) public {
      addr.transfer(testVal);
         }
   function deposit() payable public{}
}

When I am estimating the cost of the testFunc() function using truffle console, I am not getting 2300 instead I am getting 32201.

Truffle(development)> TGC= await TransferCost.new()
undefined
:
:

truffle(development)>  balance = await web3.eth.getBalance(TGC.address)
undefined
truffle(development)>  web3.utils.fromWei(balance, "ether")
'194'


truffle(development)> await web3.eth.getGasPrice()
'20000000000'

truffle(development)> await TGC.testFunc.estimateGas('0x515f013CfC0B1beA8C4B95Baa438258EA1D81eeA')
32201

Somebody please guide me how can we calculate the cost of Solidit's 'transfer' function to be 2300 Ether?

Zulfi.

Answer 1

estimateGas estimates the cost of the whole transaction, not just one line of code.

For better understanding how gas cost work, I suggest you study the generated EVM bytecode and then you can even map each VM instruction to its cost by hand.