The BRD app does not charge any fees to send a transaction. However, the ethereum network requires a "transaction fee". The cost of this fee varies as the price of the ether changes and the congestion on the network increases.

When sending a transaction, you need to make sure that you have enough funds in your wallet to cover the necessary transaction fee. Otherwise, an “Insufficient funds” error occurs.

If sending ether or ERC20 tokens, fees are not calculated by the amount of money you are sending but rather by the complexity of your transaction.  

ERC20 token transactions require a transaction fee paid in ether.