I don't know your marketplace... so I don't know whether it is, indeed, typical for seller to pay the transfer tax. Transfers taxes are typically local... city by city. There may be mitigating circumstances.
Maybe you were in a multiple offer situation, maybe the property we underpriced and in high demand. We don't know the particular details of this transaction to tell you whether this is misconduct, or your Realtor taking good care of you.
Either way, the Realtor should have had a conversation with you, informing you of the options, and offering you the choice.