What is the exchange processing fee for finra?

Excuse me, could you kindly clarify what the exact exchange processing fee is for FINRA? I'm interested in understanding the financial implications involved when engaging with the Financial Industry Regulatory Authority for any transactions or services they may provide. Is this fee a flat rate or does it vary depending on the nature of the transaction? Additionally, are there any hidden costs or surcharges that I should be aware of? I appreciate your assistance in shedding light on this matter.