How much does the Sentinel program cost?

I'm curious about the Sentinel program and its pricing structure. Could you please elaborate on how much it costs to participate in the program? Is there a one-time fee or are there recurring charges involved? Additionally, are there any hidden costs or additional expenses that I should be aware of? Understanding the financial aspect of the Sentinel program is crucial for me to make an informed decision about whether it aligns with my budget and financial goals.