Compare the cost of the transaction to the price paid. First parse the payment amount from the client and store in in a bad region of memory. Then compare that variable with the transaction amount. When you read from the variable it will be corrupt and not match. Log the Error as High Priority because it shouldn't occur. Just saved you a ton with a simple if statement.
No the price of the transaction is the sum of the items in your shopping cart which is usually stored as a session variable or cookie. The price paid is the value charged to a customer which is gathered from an input parameter on form submission. If you are attempting to bill someone 1000$ for an item that cost 10 then you have a problem. You should know what the value of every item in your inventory is right? And you should also know when said item is being purchased if you are charging someone for it. If you didnt do this check what's to stop someone from submitting a payment of 10$ for a product that cost 1000$? Your fancy system with ECC Ram would let it go through and you just lost 990$ because you thought hardware could fix your software mistakes.
This is a ridiculous conversation because data corruption could happen in the CPU cache, the QPI, or a number of micro-components in between the ram and cpu that could cause errors that ECC Ram can't fix. ECC ram is not a catch all for poor programming and poor validation checking period.
