You don't need to be an economist to shop something.  I just did some quoting of USD to EUR

 * The daily wholesale close: **1.1251**

 * The daily rate from Visa: **1.121988**

 * The quote from my brick and mortar bank: **1.1794**

 * The quote from the Travelex to pick up at my local international airport: **1.2335**

For starters, you don't get the wholesale price in a retail setting (this should be painfully obvious but I'm pointing it out anyway).  The bank is better than the airport but both are slightly worse than Visa is quoting.

I have a checking account with a Visa debit card that refunds ATM fees and doesn't charge a foreign exchange fee ***but***  I wouldn't land in a foreign country without some local currency in my pocket, so I disagree with the comment that prompted this question. I would absolutely carry $500 worth of a local currency even though it will cost 4.9% more to order it from my bank than Visa is charging today.  That's not a scam that my bank is running; it's a very valuable service and is less expensive than the currency exchange at the airport which is ***also*** not a scam.  It's literally no different than a convenience store charging more for a soda than the market does than the wholesaler does.

But, I'd also carry my $0/0% foreign exchange fee debit card and a $0/0% foreign exchange fee credit card to handle general spending, and as that comment points out the Visa exchange rate is the best of the options available at retail in my quick search.