When calling a smart contract function, who gets paid and how much does the caller pay?

Question

This is an extended question to What is "gas" and transaction fee in Ethereum?.

Who gets paid and how much does the caller pay?

Let's make some assumptions:

• There is a function F which costs 1,000 gas;
• There are 2 miners, M1 and M2;
  • Their gas prices are 1 GWei/gas and 2 GWei/gas respectively;
• There is an external address A.

The questions are:

• When a caller A invokes F, how much does A need to pay (ignoring data transfer fees)?
• Is it the total (3 kGWei) or is it determined by whoever mines it first (1 kGWei or 2 kGWei)?
• If M1 mines it first, will M2 just trust the result or will it do it all over again to check the correctness?
  • Then M2 should also get paid, right?
• Will the result be stored in all full nodes, or just the miner nodes, or just the miner nodes that are "willing" to store it (with matching gas price)?
  • Then other nodes should get paid too?

Answer 1

A specifies a gas price.

M1 and M2 decide whether to mine A's transaction if the gas price is high enough. If A's gas price was 1.5 GWei/gas, then only M1 would choose to mine A's transaction (since M2 wants 2 GWei/gas).

A always pays 1000 (given F costs 1,000 gas) multiplied by the gas price it specified; miners cannot change the transaction fee A pays and can only choose whether to include A's transaction in a block.

Only the winning miner gets the transaction fee paid by A. Other miners and all other (full) nodes do have to verify the transaction and store its results: yes, it's unfair to them and part of the problem related to incentives and scalability.

More information, https://blog.ethereum.org/2014/02/01/on-transaction-fees-and-the-fallacy-of-market-based-solutions

For each individual transaction that a miner includes, the costs are borne not just by that miner, but by every single node in the entire network.