Marcin Lipka, analyst of Cinkciarz.pl, has confirmed that it is the least profitable to exchange currencies in a bank. The difference between buying and selling price is often over a dozen groszy concerning euro or dollar. In a tradictional exchange office the difference is usually from 5 to 8 groszy - Lipka explains. But prices in the currency exchange offices online are even more profitable. The spread rate there contains mostly in the range of 1 to 2 groszy.