Shekalim, Chapter One, Mishnah Six
The rabbis added onto the half-shekel a surcharge which is called a kalbon.
Rabbi Meir and the other rabbis disagree over the nature of the kalbon and therefore over who has to pay it. According to Rabbi Meir everyone who gives the shekel has to pay the kalbon. Rabbi Meir reasons that the kalbon is a surcharge because they coin he is giving is probably not as pure as the coin demanded by the Torah. Hence, there is always an obligation to give the kalbon.
The other sages understand the kalbon to be a surcharge because when he gives a coin they will have to exchange it with a moneychanger. Therefore they hold that anyone who gives his half-shekel in one coin to the Temple need not give the kalbon, because there is no exchange. If two together give one shekel then the two must add one kalbon, because had they split their coin into two, they would have had to pay the moneychanger. The sages decreed that the money saved by not giving it to the moneychanger should go to the Temple.
In our mishnah and in the following one we learn some details about who pays the kalbon.
1) The following are liable [to pay] the kalbon (surcharge): Levites and Israelites and converts and freed slaves; but not priests or women or slaves or minors.
2) If a man paid the shekel on behalf of a priest, or on behalf of a woman, or on behalf of a slave, or on behalf of a minor, he is exempt.
3) If a man paid the shekel on his own behalf and on behalf of his fellow he is liable for one kalbon.
a) Rabbi Meir says: two kalbons.
4) If one gave a sela and received a shekel, he is liable to pay two kalbons.
Section one: This is the same list that appeared above in mishnah three with regard to taking pledges. The kalbon was paid only by those from whom they took pledges in order to collect the half-shekel. The kalbon was not taken from those who dont owe the half-shekel in the first place. The one exception may be the priests, whom according to our mishnah do not pay the kalbon. Albeck explains that the priests were lenient on themselves. Another explanation might be that this mishnah goes according to Ben Bukri in mishnah four who said that priests do not have to give the half-shekel. Finally, there are some manuscripts that do not have the word priest in this mishnah.
Section two: Since the person for whom the shekel is being paid is exempt, the one who pays it on their behalf is also exempt.
Section three: The first opinion is that of the sages, which I explained in the introduction. They are only liable for one kalbon because only one exchange was made. Rabbi Meir holds that everyone is always individually liable for a kalbon. Hence, if one person pays on behalf of him and another person, he must add two kalbons.
Section four: In this case a person gives the Temple treasurer a sela, which is the value of a Torah shekel. This is twice the amount he needs to give. He takes back in change a mishnaic shekel, which is a Torah half-shekel. In this case he must pay a kalbon for the shekel he gave and for the shekel he took, since both exchanges carry surcharges. We see from here that high banking fees are no modern invention!