What Is the Concept of ‘Economic Finality’ in Relation to the Cost of a 51% Attack?

Economic finality refers to the point at which the cost to reverse a transaction (via a 51% attack) exceeds the potential profit from the double-spend. For a cryptocurrency exchange, this means requiring enough confirmations so that the cost of renting the necessary hash power to rewrite the chain is greater than the value of the deposited funds.

This makes the attack economically irrational.