BitGo charges a transaction fee per outgoing transaction of 0.25% of the amount being transacted.
Additionally, mining fees are charged on all transactions. Mining fees vary according to overall transaction volume on the blockchain, and the fee rates are based on the physical size of each transaction, which can vary according to the number of inputs required to build the transaction and the number of outputs (recipients) the transaction is being sent to.
Mining fees can be modified in a transaction by selecting "More Options" on the transaction screen, which makes the Priority field available. The default priority on all transactions is "High"; changing this to a lower priority setting will reduce the mining fees for the transaction, but it will also increase the amount of time it takes for a transaction to confirm on the blockchain. During periods of high transaction volume, setting the Priority to "Low" or "Very Low" might result in transactions taking weeks to confirm.