All tokens on Omni Layer requires a transaction service fee in bitcoins in order to be processed and added to the Bitcoin blockchain. All Haitian Dollars Transaction is a Bitcoin transaction, just with special data in the output. Omniwallet uses about 0.00002730 BTC (2730 satoshis) for each of these non OP-Return outputs. So in order to send Haitian Dollars, you need 0.00002730 for encoding Omni outputs + a miners fee (Omniwallet currently utilizes a dynamic calculation to determine the most effective mining fee for your transaction based on the current network conditions). In more complex transactions, some of these outputs are part of a multisig output (your sending address is always one of the outputs) part of this cost is recoverable, per Omni Layer. Omni Layer states that they are currently working to make redeeming these costs easier for you.