During Old Testament times, goods, produce, livestock, and precious metals were used as currency and bartering tools. By the time of the New Testament, however, actual government sanctioned coinage became the standard form of currency and three types existed: coins which were locally minted within a given region, imperial Roman coins, and Greek coinage from the cities of Antioch and Tyre.
With so many foreign traders and Jewish pilgrims from outlaying areas, the inhabitants of Jerusalem utilized a wide variety of currency. However, because the Jews only accepted their own locally struck coins for the Temple Tax and/or donations, money changers were needed to exchange Jewish coins for foreign ones. Generally the money changers kept back a small percentage during each transaction as a surcharge for their livelihood. Because it evolved into such a viable and lucrative business, stiff competition naturally arose which, not only increased the number of money changers but, caused them to compete for available space in and around the Temple – especially during the busy holiday seasons. Unfortunately, some persons began to enter this business with the outright intent of cheating people who had little knowledge of what their foreign coins were worth, thus perhaps creating the first instances of “money fraud” and “white collar crime!”
The fact that these money changers were so business-minded, competitive, unscrupulous, and loud were just some of the reasons why Christ so feverishly chased them out of the Temple.