Although you have not been asked, someone could ask you to justify your fees, pay or return. You would have to conduct a cost study and you will find that the cost is a little less when a check is paid with that result ending the process. Returned checks continue to cost you money as they travel back through the system, e.g. float, FRB charges, possible corresponding bank charges, DP charges, etc.
If your pay fee is less than your return fee, you are in great shape to have a cost study support the fees. On the other hand, simply due to the fact that they are the same at most institutions does not mean that much as a cost study may reveal that the return fee is providing a break to the customer.
You simply need to be sure that your fees are aligned with other institutions in your community.