I paid by bank wire, why was the amount added to my account less than the amount I sent you?

If a wire needs to pass through an intermediate bank to reach our account, sometimes that bank charges a fee to process the wire transfer. This is especially true in the case of international wire transfers.

"Every intermediate bank that handles a transaction can take a fee directly out of the wire payload (the assets being transferred) without the account holders knowledge or consent. There is no legislation or technical means to protect customers from this practice. If bank S is the sending bank (or brokerage), and bank R is the receiving bank (or brokerage), and bank I1, I2, and I3 are intermediary banks, the client may only have a contract with bank S and/or R, but banks I1, I2, and I3 can (and often do) take money from the wire without any direct arrangement with the client. Clients are sometimes taken by surprise when less money arrives at bank R. Contrast this with checks, the amount transferred is guaranteed in full, and fees (if there are any) can only be charged at endpoint banks."

Wikipedia Reference