How much does protocol IO cost?

Could you please elaborate on the pricing of protocol IO? I'm particularly interested in understanding the cost associated with adopting or utilizing this protocol within my financial or cryptocurrency endeavors. Is there a fixed fee, or does the cost vary depending on factors such as usage, transaction volume, or other metrics? Additionally, are there any hidden costs or ongoing fees that I should be aware of? Clarifying these details would greatly assist me in evaluating the feasibility and cost-effectiveness of incorporating protocol IO into my operations.