The last time this story made its rounds (and if this is the same guy), he was overcharging by about 10%.
So if you buy a $10 pizza, you'll pay the equivalent of $11. Waiting in line at the bank takes more than $1 of my time. And I don't know if banks give their best rates to folks who aren't account-holders, or even if they do the exchanges at all for folks who aren't their customers.