Utilize your financial knowledge, give your answer or opinion to the input question or subject . Answer format is not limited.

Why do financial institutions charge so much to convert currency?
Is there not some central service that tracks current currency rates that banks can use to get currency data? Sure.  But this doesn't matter.  All the central service can tell you is how much the rate was historically.  But the banks/PayPal don't care about the historical value.  They want to know the price that they'll pay when they get around to switching, not the last price before the switch.  Beyond that, there is a transaction cost to switching.  They have to pay the clearinghouse for managing the transaction.   The banks can choose to act as a clearinghouse, but that increases their risk.  If the bank has a large balance of US dollars but dollars are falling, then they end up eating that cost.  They'll only take that risk if they think that they'll make more money that way.  And in the end, they may have to go on the currency market anyway.  If a European bank runs out of US dollars, they have to buy them on the open market.  Or a US bank might run out of Euros.  Or Yen.  Etc.   Another problem is that many of the currency transactions are small, but the overhead is fixed.  If the bank has to pay $5 for every currency transaction, they won't even break even charging 3% on a $100 transaction.  So they delay the actual transaction so that they can make more than one at a time.  But then they have the risk that the currency value might change in the meantime.  If they credit you with $97 in your account ($100 minus the 3% fee) but the price actually drops from $100 to $99, they're out the $1.   They could do it the other way as well.  You ask for a $100 transaction.  They perform a $1000 transaction, of which they give you $97.  Now they have $898 ($1000 minus the $5 they paid for the transaction plus the $3 they charged you for the transaction).  If there's a 1% drop, they're out $10.98 ($8.98 in currency loss plus a net $2 in fees).   This is why banks have money market accounts.  So they have someone to manage these problems working twenty-four hours a day.  But then they have to pay interest on those accounts, further eating into their profits.  Along with paying a staff to monitor the currency markets and things that may affect them.