What is STP cost?

Could you please elaborate on the concept of STP cost? I'm particularly interested in understanding its application within the cryptocurrency and finance landscape. Specifically, how does STP cost differ from traditional transaction fees or costs? Is it a one-time fee or a recurring cost? Additionally, what factors influence the calculation of STP cost, and how does it impact the overall efficiency and profitability of transactions? Your insight into this matter would be greatly appreciated.