Interview coaching/Mock interviews

Hi everybody
I am in the process of preparing for a Amazon TPM interview, senior/principal/staff , whichever is most senior, and as part of this process, I have been reading on the LP principals, preparing stories in the STAR format. As part of this search/investigation, I came across multiple youtube channels, multiple pages and multiple coaching options. I think I need coaching and reached out to two that I like so far, and the experience has been interesting to say the least, one only shared the first name, she/he will not share a Linkedin profile or anything but offers 200$ review session, I pinged him and he says he is not comfortable to share his details with strangers, which is ok, but he will all of mine, and I do not even what/who i am taking to. Another person, runs a youtube channel as well, and offers a membership 2k per month or so, she also is ex amazon , so contacted her to talk before I sign up and the message I got I do not talk in person/consultation calls. How can one sign up for 200$ an hour and 2k per month without even know anything? They are a million sites out there saying coaching how do we know what is a good fit ? Is this expected or did I hit on something rare ? Did anybody mock interviews/coaching as part of their prep ? Any pointers? I just find it odd, I openly agree these channels are good, and I like them but it is common to ask for a review or talk before one signs up or reach out to other customers no ?? Thoughts / pointers in my prep ?? Appreciate your input in advance. Tx. Note: I also found Pramp as part of this process, did anybody try that ?