5 Seconds after you complete your transaction: the money leaves your account.
5 secs to 2 days after: The bank is holding onto the money while they check all the information/credentials, make sure its all legit, go through federally mandated safety measures, etc. It might be more accurate to say that 5 seconds after you complete your transaction, an authorization hold is placed for the value the merchant submitted. Your ledger balance isn't updated until the completed transaction posts, but the "available balance" your bank gives you includes the value of that hold.
2 to 3 days after: The merchant actually receives the money.
Now, just apply that in reverse for refunds. 5 seconds after the transaction, the money has left the merchant's account, then the bank does a day or two of processing, and then, 3 days later, you finally get the money.
It only LOOKS like its done in 5 seconds for payments, and takes 3 days for refunds, because you're only seeing your end of things. You're not seeing the middle part of processing or the merchant's end of things.
